Add unit tests for cinder/api/contrib/volume_actions.

Added to the following unit tests:
  Test begin detaching;
  Test roll detaching;
  Test volume upload to image with TypeError;
  Test extend volume with ValueError;
  Test copy volume to image, when body without Image's name.

Change-Id: I2382e043b7968a2c285c505ec02ff65fd81ea605
Merge "Add unit tests for cinder/api/contrib/volume_actions."