Use SolidFire snapshots for Cinder snapshots

Use SolidFire snapshots for Cinder snapshots

This patch just replaces the use of clones on the SolidFire
backend for SolidFire Snapshot objects.  This isn't necessarily
an issue, but it is important necessary to do things like
consistency group snaps.

Note, that we have to keep compatability for things like
create_from_snapshot where the system may have clones that
were used for snapshots prior to updating the driver.

While we're here, we also removed the logging calls in the test
which shouldn't really be there, as well as the overly chatty
debug messages like "entering/leaving".  More cleanup work
can be done to logs but should be in their own patch.

Change-Id: Ia67b2b9e3c0bf3b0b1f991e958f8eac13830f9cc