Add a comment and a spec to misc:multi_call/4.
Add a comment and a spec to misc:multi_call/4.

Change-Id: Ie6723d4adb7af5fad67f9f9db34b99a2ba14d306
Reviewed-on: http://review.couchbase.org/70214
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

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