turned ns_janitor timeouts to milliseconds

For consistency

Change-Id: Ie5a07170f29b70aa6aa59cad7566d4249df26c4d
Reviewed-on: http://review.couchbase.org/40633
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>