Add a config heartbeat mechanism that's configurable

Change-Id: Iaf28a86049e69c9fa24f1cbc47cae21b1c0cbb07
Reviewed-on: http://review.couchbase.org/41799
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>