Add exception catch if Storwize/SVC driver failed when
retyping

If adding a copy for a volume of Storwize/SVC which is under
migration, Storwize/SVC command will fail because the
number of the copies of the volume exceed the limit which
is 2.

Modifying the volume type when adding a copy for the volume,
Storwize/SVC driver will also fail, should add exception catch.

Also add exception catch when getting the volume from the database.
This change is necessary to enable resolving bug 1305550
(https://bugs.launchpad.net/cinder/+bug/1305550 - Failed retype with
driver raised exception should set volume status to "error" ).

Change-Id: I1cf4b6606b5228c8adcb2bde21f345fa979bc13e
Closes-Bug: #1298201
Merge "Add exception catch if Storwize/SVC driver failed when retyping"