engine: Update gluster task's info only if job in progress

Whenever status of remove-brick or rebalance is
queried, the corresponding step information
is updated.
Fixed to do this only for in progress jobs

Change-Id: I8e431da7797911372f8b6e474a4ab74c6626366d
Bug-Url: https://bugzilla.redhat.com/1061725
Signed-off-by: Sahina Bose <sabose@redhat.com>