bp:MB-5307: hibernate menelaus_web:handle_streaming processes

This is backport of part of 6b852764e5f51d4a4c5c716025ff9eb485c51bbd

Erlang is not very eager on GC-ing those processes that just sit there
and wait config updates. We know that consuming config via
ns_config:get instantly eats lots of ram, so hibernating really helps
a lot.

Change-Id: Ifcf49af061d82bf68b97c02c306e7233170c0102
Reviewed-on: http://review.couchbase.org/24783
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>