CBQE-0: Increase timeout after warmup to reduce Memcache errors

Change-Id: I063dc0890bcd6b1e7c6c16e66f1d1b40bcb631a9
Reviewed-on: http://review.couchbase.org/36406
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Aruna Piravi <aruna@couchbase.com>