CBQE-2075: added support for XDCR pause and resume for tests

Change-Id: I6dadbb9085cccf5a8da2525811dd4f93208e29ea
Reviewed-on: http://review.couchbase.org/33904
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>