MB-10650 kill auth cookie on browser after logout

Change-Id: I587651f9e3f84a4015fad29aebda8f2d3761d541
Reviewed-on: http://review.couchbase.org/35921
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>