Refactored logic to select blockdevice which is unclaimed and does not contain any file system into it

[amitbhatt818]

Why this PR required?

• Sometimes filesystem is getting created into the master node blockdevices.
• And when we are using that device we are getting an error saying.

  TASK [Create CSPC] *************************************************************
  fatal: [127.0.0.1]: FAILED! => {"changed": true, "cmd": "kubectl create -f /utils/cspc.yml", "delta": "0:00:00.184331", "end": "2020-07-16 07:47:28.302378", "msg": "non-zero return code", "rc": 1, "start": "2020-07-16 07:47:28.118047", "stderr": "Error from server (BadRequest): error when creating \"/utils/cspc.yml\": admission webhook \"admission-webhook.cstor.openebs.io\" denied the request: invalid cspc specification: invalid pool spec: block device has file system {ext4}", "stderr_lines": ["Error from server (BadRequest): error when creating \"/utils/cspc.yml\": admission webhook \"admission-webhook.cstor.openebs.io\" denied the request: invalid cspc specification: invalid pool spec: block device has file system {ext4}"], "stdout": "", "stdout_lines": []}

Solution:

• This PR helps in selecting block device name which doesn't have and filesystem into it.

Signed-off-by: Amit Bhatt amitbhatt818@gmail.com