Create resources using wrapper utility

It is more efficient to use cls.create_volume and cls.create_snapshot
methods from BaseVolumeTest class for resources creation. There is an
advantage that these methods are synchronized with resource_cleanup,
therefore, resource_cleanup method in the tests class is redundant.

Change-Id: Iea8f430982826f84ef2eef4e886cca3c9b966366
1 file changed