Add Galera packages to container image

[jcpowermac]

It would be great if the image had installed the galera packages even if it wasn't configured.
Then I wouldn't need to do something like this:

https://github.com/jcpowermac/mariadb-ha-poc/blob/b7df7f4ec06bac5127ae9bd46a3ea76a25f9a512/mariadb-galera-ephemeral-template.yml#L195-L204

The configuration can be handled using S2I (which is very cool btw).