Add branch-tynset.xml for tighter bucket density

Change-Id: Ie403208bfc3b48945b22a807ad167c1b65b7ea0e
Reviewed-on: http://review.couchbase.org/40779
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>