Remove "service" from required_import_options
Remove "service" from required_import_options

In the backup import record API, The "service" property is
always overrided by the backup driver. So this perperty which
sent by users is useless and should not be required.

Change-Id: If8fe0d7c385b89ca82442b3d273b39216de87ec8

j-griffith/cinder,Datera/cinder,phenoxim/cinder,Datera/cinder,eharney/cinder,mahak/cinder,openstack/cinder,eharney/cinder,openstack/cinder,phenoxim/cinder,ge0rgi/cinder,j-griffith/cinder,mahak/cinder