flake8 H202 error in test_image_utils.py

H202 will detect following case:
self.assertRaises(Exception, foo)

Replace Exception with test.TestingException to pass the H202 checking.

Bug #1214365

Change-Id: Idbd13d11995e6a22e99bb9d63c344a5b1a75f987
GPFS use clone_image for creating volumes

If both source and target of gpfs create volume from image operation
are backed by gpfs storage use clone_image method for implementing
the move of image data to the new volume.

The copy_image_to_volume method is used only if this is not true,
and uses image_utils.fetch_to_raw to move image data to the new
volume.

Fixes bug #1213248

Change-Id: I3958febe67cc86bc3cb608288f7d064f74d3a731
Move root task class to base file.

Start cleaning up the large create_volume file by
splitting up the base task and task naming helper
into its own file.

Change-Id: Ibff80dc8b10507d49374737b4760039f51d8e1ba
Merge "Move root task class to base file."
Merge "GPFS use clone_image for creating volumes"
Merge "flake8 H202 error in test_image_utils.py"