bug 2521 - avoid locks around front cache & set optimization
bug 2521 - avoid locks around front cache & set optimization

Check the config/behavior flags before accessing locks, as an
optimization when the front cache & set optimization are configured
to be off.

Change-Id: If6333fc63f08bca927dedfa17bc4eaa8eb3f06bd
Reviewed-on: http://review.northscale.com/2771
Tested-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>
Tested-by: Matt Ingenthron <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@northscale.com>
Reviewed-by: Matt Ingenthron <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@northscale.com>

membase/moxi,couchbase/moxi,couchbase/moxi,couchbase/moxi,couchbase/moxi,membase/moxi,membase/moxi,membase/moxi,zbase/moxi,zbase/moxi,couchbase/moxi,membase/moxi,zbase/moxi,membase/moxi,zbase/moxi,zbase/moxi,couchbase/moxi