* Adds custom_data parameter to azure virtual machine resource
Invoke custom_data in an integration test: This invocation of
custom_data should not cause any side effects.
* Bugfix: String encoding now works in both python2 and 3
* Fix pep8 violations
* Use nginx to serve a text file created via custom_data and verify that
that custom_data is working
* fix up azure_rm_virtualmachine custom_data
* tweaks #25924
* simplify string encoding fun
* don't rely on external packages
* add availability set for vm
* add test
* add import
* fix
* add test assert and output
* fix lint and version added
* add null check
* fix mirror
* fix mirror
* azure_rm_virtualmachine: added support for specifying custom image
* Use separate parameter for custom_image, add very basic test
* missed the version_added tag for doco
* removed whitespace I accidentally left in
* merged custom image into the image dict and added more tests
* added one more test
