MB-100: fix Errno 32 in incremental_rebalance_out_with_ops

Change-Id: I0f77e68d43677c75940cc51f5a23e091404fbc85
Reviewed-on: http://review.couchbase.org/25586
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>