Catch volume create exception

Catch InvalidInput exception from cinder when the parameters
are invalid such as an invalid size. Currently the exception
is not caught which results in a 400 Bad Request correctly being
returned, but also leaving a traceback in the logs. Correctly
catching the exception and explicitly raising an HTTPBadRequest
removes the production of the traceback

Fixes bug #1098048

Change-Id: Ia66e67f302cf20e96417f4ff3c1430b755a4a861
Merge "Catch volume create exception"