code refactory

* adding max parameter to a command instead of writing different tests for each option of the command
* instead of querying for image for each vm create i'm storing imageid in env var(first time image id is queried from azure and is stored in env)
* removing commands where results are obvious whereever possible (like ex in extension set and disable you don't have to do extenstion set extension get extension disable andextension get again instead set extension disable and get extension)