MSFT_xPackageResource: Fix PSSA Issues

[kwirkykat]

The PowerShell Script Analyzer issues in MSFT_xPackageResource need to be fixed.
This is the current result of running Invoke-ScriptAnalyzer:

[kwirkykat]

The error here is fixed in #123

[kwirkykat]

This is part of #160

[PlagueHO]

I'll work on this one if you like, because I need to get a fix through for #52.

[PlagueHO]

I'm working through these and am finding that there is some contention over whether or not the PSUseShouldProcessForStateChangingFunction warning should actually be used:
PowerShell/PSScriptAnalyzer#283

My feeling is that this warning:

1. doesn't make a lot of sense when it is reported in Unit/Integration test code.
2. isn't helpful in the context of DSC Resources
3. is often a false positive

Therefore I would propose that this warning is simply suppressed when it occurs in any Unit or Integration tests in any of these modules.

[kwirkykat]

@PlagueHO Yes agreed on that rule. Just posted the PSSA rule severity list for DSC Resource Kit.
That should help with what rules are allowed to be suppressed/not suppressed.

Haven't implemented this list in tests yet though.
There has been a lot of update to this file since I submitted this issue. This is now the current output of PSSA after #192 is merged:

^Note in this case it would be approved to suppress the PSSA rule 'PSAvoidGlobalVars'

[PlagueHO]

@kwirkykat - oh nice! Good idea on the PSSA List.

As for the remaining rules, those are the only ones I've fixed. I noted the suppression of the PSAvoidGlobalVars one too. I'll submit my PR sometime today/tonight.

Thanks for getting back to me so quick. I'll also get some other PRs through for the warnings on the other resources.