glusterfs: Honor mount options when restarting cinder service

When restarting cinder service (cinder-volume specifically),
ensure that the gluster mounts are unmounted and remounted so
that any new mount options added to the shares config file
is taken effect, post service restart.

Change-Id: I9fe3442cd4899770b4c9ea4a73a7fe62967f2c64
Merge "glusterfs: Honor mount options when restarting cinder service"