Several azure fixes/improvements, including:
* Improve failure message when python-azure is not installed
* Improve required argument handling
* Fixes a traceback on instance termination when the variable
'deployment' was not set.
* Fixes a traceback (#8298) when creating instances using the newer SDK
* Fixed error messages to be more descriptive
* Removed direct use of subprocess module and replaced it with calls
to module.run_command
* Changed AZURE_MANAGEMENT_CERT_PATH to be just AZURE_CERT_PATH, which
matches what is expected by the inventory script
