engine: update the rebalance task status correctly in stop rebalance

updating the rebalance task status using the rebalance
status returned from stop rebalance vds command.

Change-Id: I2a689db9a7651a5a48e1ffea70fc59431554e2bc
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1019598
Signed-off-by: Ramesh Nachimuthu <rnachimu@redhat.com>