Add images exceptions

*Added exceptions module for images

Change-Id: I64a34a7758533c830d57107670c1bfd3b9a594f2
Update images behaviors

*Updated tasks related methods
*Updated create image method names for better clarity
*Corrected missed create image call
*Removed passing  client to wait_for_task_status
*Updated all None checks to use shorthand notation
*Updated white space to be more consistent
*Updated validate_task validation efficiency

Change-Id: I1e1f986cfc86a6eeb8d7b93b0df306fee6e58e6b
Merge "Update images behaviors"
Merge "Add images exceptions"