CBQE-0: fix _offline_upgrade for xdcr

Change-Id: I5d92267e1a80405e9c557747e038cd1673371c34
Reviewed-on: http://review.couchbase.org/30311
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>