Merge unit test cases for xSMB powershell support

The unit test cases covers most dev logic inside cmdlets as well as most positive scenarios and some of the negative cases which involves client side logic (e.g. naming validation).
We already has [test file](https://github.com/Azure/azure-sdk-tools/blob/dev/src/ServiceManagement/Services/Commands.Test/Common/WindowsAzureEnvironmentTests.cs) please use it.