Run Gerrit.

This role deploys MariaDB alongside the Gerrit service using
docker-compose to run both services in docker containers.
Variables below configure MariaDB connection details.

**Role Variables**

.. zuul:rolevar:: gerrit_reviewdb_mariadb_dbname
   :default: gerrit

   The database to make and connect to.

.. zuul:rolevar:: gerrit_reviewdb_mariadb_username
   :default: gerrit

   The MariaDB user to make and connect with.

.. zuul:rolevar:: gerrit_reviewdb_mariadb_password
   :default: <unset>

   The password to set for ``gerrit_reviewdb_mariadb_username``