Add Check mode support to rubrik_login_banner

[KowMangler]

Description

Please describe your pull request in detail.

Add check-mode support to login_banner module

Related Issue

This project only accepts pull requests related to open issues.

• If suggesting a new feature or change, please discuss it in an issue first.
• If fixing a bug, there should be an issue describing it with steps to reproduce

Please link to the issue here
#78

Motivation and Context

Why is this change required? What problem does it solve?

Adding this allows for "check-mode" switch to be used and returns whether the module would have made a change if the flag were removed.

How Has This Been Tested?

• Please describe in detail how you tested your changes.
• Include details of your testing environment, and the tests you ran to see how your change affects other areas of the code, etc.

Rubrik CDM 5.0.2
Ansible 2.9.8
RHEL 7.8

Screenshots (if appropriate):

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

Go over all the following points, and put an x in all the boxes that apply. If you're unsure about any of these, don't hesitate to ask. We're here to help!

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTION document.
• I have updated the CHANGELOG file accordingly for the version that this merge modifies.
• I have added tests to cover my changes.
• All new and existing tests passed.