cbqe-0: add expire pager warm up

Change-Id: Ic19448c12f4ac943233842a31eb1437215bb73f9
Reviewed-on: http://review.couchbase.org/38145
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>