CBQE-2418: add ui xdcr tests

Change-Id: I96f535e2551161bfbfbcbe728f6b8a730127eeda
Reviewed-on: http://review.couchbase.org/41776
Reviewed-by: Meenakshi Goel <meenakshi.goel@globallogic.com>
Tested-by: buildbot <build@couchbase.com>