Tune warning options

Change-Id: Ica6aea3bc80346d73dd97d4f9d2bf737ef9219dd
Reviewed-on: http://review.couchbase.org/30687
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>