fix whitespace bugs for hub and pipeline & add some negative test cases

1.	Fix whitespace name bug for pipeline/hub (Get-AzureDataFactoryPipeline -ResourceGroupName $resourceGroupName -Datafactoryname $Datafactoryname -Name "     "(only whitespaces) does not throw error for name property)
2.	Add some related test cases (both E2E and unit tests)
3.	Separate some negative tests

I tried it but it won't work if I put the stub command into Command.Resource project since if the command was there, it will only work in the AzureResourceManager Mode