variable value should del after update

[amolpati30]

I extended the existing test case to include the following steps:

1. Create an Ansible variable with a default value and an overridden key.
2. Update the value of the Ansible variable at the host level.
3. After updating, delete the value, ensuring that it reverts to the default value.

Dependent PR: https://github.com/SatelliteQE/airgun/pull/1643

[Satellite-QE]

PRT Result

Build Number: 9422
Build Status: SUCCESS
PRT Comment: pytest tests/foreman/ui/test_ansible.py::TestAnsibleCfgMgmt -k test_positive_assign_ansible_role_variable_on_host --external-logging
Test Result : ========== 1 passed, 10 deselected, 24 warnings in 817.03s (0:13:37) ===========

[Satellite-QE]

PRT Result

Build Number: 9443
Build Status: UNSTABLE
PRT Comment: pytest tests/foreman/ui/test_ansible.py::TestAnsibleCfgMgmt -k test_positive_assign_ansible_role_variable_on_host --external-logging
Test Result : ========== 1 failed, 10 deselected, 22 warnings in 793.28s (0:13:13) ===========

[amolpati30]

trigger: test-robottelo pytest: tests/foreman/ui/test_ansible.py::TestAnsibleCfgMgmt -k test_positive_assign_ansible_role_variable_on_host airgun: 1643

[Satellite-QE]

PRT Result

Build Number: 9446
Build Status: SUCCESS
PRT Comment: pytest tests/foreman/ui/test_ansible.py::TestAnsibleCfgMgmt -k test_positive_assign_ansible_role_variable_on_host --external-logging
Test Result : ========== 1 passed, 10 deselected, 24 warnings in 933.30s (0:15:33) ===========