CBQE-1053: logging timeouts in xdcr tests

Change-Id: I05ea62e676e7f545bc92d542d0757b883a1506c5
Reviewed-on: http://review.couchbase.org/24690
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>