Adding TLS 1.2 support for the PowerShell module

[MikeFal]

Description

Currently, PowerShell defaults to using TLS 1.0 for Invoke-WebRequest. This change forces use of TLS 1.2.

Related Issue

Fixes #153 RFE: TLS 1.2 support

Motivation and Context

If the Rubrik cluster disables TLS 1.0, the PowerShell module will stop working. Enforcing TLS 1.2 for the Rubrik PowerShell module solves this issue.

How Has This Been Tested?

Rubrik's SE-3 lab has TLS 1.0 disabled. With the updated module, Get-RubrikVM, Get-RubrikDatabase, and New-RubrikSnapshot were tested to validate no issues with connectivity.

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.

[chriswahl]

Tested on my end. Works fine.