MB-24493: Clear the janitor request callback...
MB-24493: Clear the janitor request callback...

...list after notifications are sent during the case the janitor
run gets interrupted.

Otherwise this would lead to sending the requestors multiple messages
when they are not expecting more than one.

Change-Id: If91599330e22b8a9cd94f86bc64dfa2e91293943
Reviewed-on: http://review.couchbase.org/78565
Tested-by: Ajit Yagaty <670a5cadfa9668cb910cc315f6527868cd5ab42a@couchbase.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server