Adds openstack-doc IRC channel configuration for gerritbot.

(Not sure I have any pre-reqs for this patch but please review
to educate me.)

Patchset gets the channel name right.

Change-Id: I7d195253bacd2188e7c82ae69ef7e1690b8835be
Reviewed-on: https://review.openstack.org/21696
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Emilien Macchi <emilien@enovance.com>
Reviewed-by: Paul Belanger <paul.belanger@polybeacon.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins