Rating lobby bot should react to closed SQL connection

[elexis]

If the SQL connection of the lobby rating bot has not been used since a while (svn lobby), the sql connection will be closed from the server:

​https://mariadb.com/kb/en/library/server-system-variables/#interactive_timeout

Then the lobby bot service is in a state where it leaves and rejoins the room everytime someone logs in and can't recover until the process had been restarted manually.

The impact can be reduced by setting the timeout value to the max. The bot ought to attempt to reconnect multiple times in exponentially increasing intervals.