Add new test that checks that channels mentioned in gerritbot are also
in accessbot.
Enhance the irc tox target so that it runs the checks, and update Zuul
so that the job is run for changes to gerritbot.
Add channels openstack-mistral and puppet-openstack to accessbot,
openstackinfra now has access to the channels. These two channels are
already in gerritbot.
Make check_irc_access.py script executable.
Change-Id: Ic68ba9a1c60854e68817fcadb1a5df2144944af7
f8788e2e27