Cannot execute mock for Get-PackageSource cmdlet

[nohwnd]

In order to fix Get-PackageSource cmdlet, another level of indirection was introduced which broke other things.

Original issue and PR:
#1308
#1317

Issue it caused and revert PR:
#1519
#1528

[nohwnd]

@renehernandez I reverted the change, because from what I understand it only affects Get-PackageSource cmdlet which is not a blocker for release. If you'd have time please take a look.