Fix validate_role_spec for nested spec

[ganeshrn]

Fixes https://github.com/ansible-network/network-engine/issues/189

• Adds support to validate nested subspecs for conditional like mutually_exclusive, required_if, required_one_of and required_together.
• Returns the expanded role spec params initialized with default values as result of validate_role_spec task, this result can be used in later task to set the expanded role spec variables to it's default value

eg Playbook:

---
- hosts: localhost
  connection: local
  gather_facts: no
  vars:
    mlag_setup:
      peer: test
      ipaddr: value
  tasks:
  - name: set role path
    set_fact:
      role_path: ../ansible-network.network-engine

  - name: import role
    import_role:
      name: ../ansible-network.network-engine

  - name: validate spec
    validate_role_spec:
      spec: mlag_setup_spec.yaml
    register: role_spec

  - name: set role params
    set_fact:
      "{{ item.key }}": "{{ item.value }}"
    loop: "{{ lookup('dict', role_spec.role_params, wantlist=True) }}"

  - name: print role variables
    debug:
      msg: "{{ mlag_setup }}"

Contents of spec file:

$ cat mlag_setup_spec.yaml
---
argument_spec:
  mlag_setup:
    type: dict
    options:
      state:
        type: str
        required: false
        default: present
        choices:
          - "present"
          - "absent"
        description:
          - "Desired state: present, absent"

      peer:
        type: str
        required: true
        description:
          - "The MLAG peer switch hostname (inventory_hostname)"

      vlan:
        type: int
        required: false
        default: "4094"
        description:
          - "VLAN to use for peer communication."
          - "VLAN is used to create the interface vlan for MLAG_CONTROL_PLANE."

      domain:
        type: int
        required: false
        default: "1"
        description:
          - "Represents the MLAG domain."
          - "The ID must be the same only for members of the same MLAG domain."
          - "Domain is used to create the MLAG_CONTROL_PLANE VRF with RD <site>:<domain>"

      site:
        type: int
        required: false
        default: "1"
        description:
          - "Represents the site where the domain is located."
          - "Site is used to create the MLAG_CONTROL_PLANE interface with address 169.254.<domain>.<site><device>"
          - "Site is used to create the MLAG_CONTROL_PLANE VRF with RD <site>:<domain>"

      device:
        type: int
        required: false
        default: "1"
        description:
          - "Unique ID to represent the device member of the MLAG domain"
          - "The ID is used to create the peer communication address 169.254.<domain>.<site><device>"

      linkagg:
        type: int
        required: false
        default: "1"
        description:
          - "Linkagg to use for the peer-to-peer communication."

      vlans:
        type: list
        required: false
        default:
          - "all"
        description:
          - "List of vlans member of the MLAG domain"
          - "VLANs are NOT created if they do not exist"

      interlinks:
        type: list
        required: false
        default:
          - "Ethernet1"
        description:
          - "List of physical interfaces used by linkagg as interlinks for the peer-to-peer communication"

      heartbeat:
        type: int
        default: "10000"
        required: false
        description:
          - "Timer for heartbeat in ms"

      reload_delay:
        type: int
        default: "150"
        required: false
        description:
          - "Delay to bring MLAGs up after reload."
          - "Helps to ensure that MLAGs comes up only when adjacency is done and tables are pre-populated."
          - "Prevents blackhole of traffic when device is converging and tables being populated after a reboot."

      ipv4:
        type: str
        required: true
        description:
          - "IPV4 address to use for the MLAG intercommunication"
        aliases:
        - ipaddr

      vrf:
        type: str
        required: false
        default: "mlag_control"
        description:
          - "The VRF name for the MLAG intercommunication"

      extension:
        type: dict
        required: false
        description:
          - "Extension of specs with platform-specific keys/values"

Ansible run output logs:

PLAY [localhost] ***********************************************************************************************************

TASK [set role path] *******************************************************************************************************
ok: [localhost]

TASK [validate spec] *******************************************************************************************************
ok: [localhost]

TASK [set role params] *****************************************************************************************************
ok: [localhost] => (item={'key': u'mlag_setup', 'value': {u'domain': 1, u'interlinks': [u'Ethernet1'], u'extension': None, u'vlan': 4094, 'ipaddr': u'value', u'site': 1, 'peer': u'test', u'state': u'present', u'vrf': u'mlag_control', u'reload_delay': 150, u'device': 1, u'heartbeat': 10000, u'vlans': [u'all'], u'linkagg': 1, u'ipv4': u'value'}})

TASK [print role variables] *********************************************************************************************************
ok: [localhost] => {
    "msg": {
        "device": 1,
        "domain": 1,
        "extension": null,
        "heartbeat": 10000,
        "interlinks": [
            "Ethernet1"
        ],
        "ipaddr": "value",
        "ipv4": "value",
        "linkagg": 1,
        "peer": "test",
        "reload_delay": 150,
        "site": 1,
        "state": "present",
        "vlan": 4094,
        "vlans": [
            "all"
        ],
        "vrf": "mlag_control"
    }
}

PLAY RECAP *****************************************************************************************************************
localhost                  : ok=4    changed=0    unreachable=0    failed=0    skipped=0

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• ansible-network-tox-py27 : SUCCESS in 3m 49s
• ansible-network-tox-py36 : SUCCESS in 3m 37s
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• dco-license : SUCCESS in 27s

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Build succeeded (gate pipeline).

• tox-linters : SUCCESS in 3m 19s
• ansible-network-tox-py27 : SUCCESS in 3m 44s
• ansible-network-tox-py36 : SUCCESS in 3m 44s
• dco-license : SUCCESS in 28s