This new ansible role deploys gerritbot with docker-compose on
eavesdrop.openstack.org. This way we can run it where the other bots
live.
Testing is rudimentary for now as we don't really want to connect to a
production gerrit and freenode. We check things the best we can.
We will want to coordinate deployment of this change with disabling the
running service on the gerrit server.
Depends-On: https://review.opendev.org/745240
Change-Id: I008992978791ff0a38f92fb4bc529ff643f01dd6
506a11f9d2