MB-100: tune cache misses

Change-Id: I368ea0727bc541bcff274ba3140380ff5325a201
Reviewed-on: http://review.couchbase.org/27475
Reviewed-by: Ronnie Sun <ronnie@couchbase.com>
Tested-by: Ronnie Sun <ronnie@couchbase.com>
Tested-by: buildbot <build@couchbase.com>
MB-100: tune cache miss

Change-Id: I5eeaf15bf2a30b783ec6463b653eb89ed7f3dfdd
Reviewed-on: http://review.couchbase.org/27477
Reviewed-by: Ronnie Sun <ronnie@couchbase.com>
Tested-by: Ronnie Sun <ronnie@couchbase.com>