Announce openstack repo merges in #openstack-oslo

Right now gerritbot doesn't announce when patches merge to
the #openstack-oslo irc channel. This patch adds a line to
the gerritbot yaml file to announce merges in all oslo repos
reporting to the #openstack-oslo channel.

Change-Id: Idea2c6fe6ee1362342b43de930f0e058e12f6dbe
Merge "Announce openstack repo merges in #openstack-oslo"