[gen_server2] Allow custom-handling job deaths.
[gen_server2] Allow custom-handling job deaths.

Change-Id: I82b244c05ac229bc6c378b45bf3cfab544deb1a2
Reviewed-on: http://review.couchbase.org/88118
Tested-by: Aliaksey Artamonau <ce14b1c16e0fd654f926118eb8addbec5aff4ffa@couchbase.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

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