Parallelize test run.
Retry Add-AzureDisk, Add-AzureVMImage and Remove-AzureVMImage during 409 error
1. Update Stop-AzureVM tests.
2. Update BVT tests
Update Add-AzureVhd and Save-AzureVhd tests when "pipeline is already running" exception happens:

https://github.com/WindowsAzure/azure-sdk-tools/issues/1812

https://github.com/WindowsAzure/azure-sdk-tools/issues/1442
Update Add-AzureVhd and Save-AzureVhd tests when "pipeline is already running" exception happens:

https://github.com/WindowsAzure/azure-sdk-tools/issues/1812

https://github.com/WindowsAzure/azure-sdk-tools/issues/1442
Merge pull request #42 from hyonholee/dev

Parallelize tests.