CBQE-1305: rebalance progress api changed

Change-Id: Iabdd950fa91a04ec673e998d33040da637bc9e38
Reviewed-on: http://review.couchbase.org/26449
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Deepkaran Salooja <deepkaran.salooja@globallogic.com>