CBQE-0: fix rebalance_out_with_ddoc_compaction stuck due to bug in CB

Change-Id: I61801e08db2f8c586cb819b3d1e2ee5ca652770b
Reviewed-on: http://review.couchbase.org/37864
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>