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

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