gluster: fix releasing lock in task sync-job

When a remove-brick start is CLI and
engine detects it and creates a job for it.
A lock is  acquired for the volume, and released.

Now the lock won't be released, the same will be
released when the task is completed.

Change-Id: Ib1934bfa976456949a475f6675866bbd083185f4
Bug-Url: https://bugzilla.redhat.com/1061677
Signed-off-by: Kanagaraj M <kmayilsa@redhat.com>