CBQE-1107: add replica read test with big value size

Change-Id: Ib2685cb234c5ace914e299e90a1d95668f8f2028
Reviewed-on: http://review.couchbase.org/25873
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>