wikistats - add mariadb-server class

meanwhile we can just install the package in labs
it seems. no more setup needed here to add external repo

but also doesn't look like we have a central server for projects
yet, so installing on localhost again for now

on old instance we had dependency errors:

mariadb-server : Depends: mariadb-server-5.5 (= 5.5.38+maria-1~precise)
but 5.5.36+maria-1~precise is to be installed

and it suggested apt-get -f install ...

Change-Id: I9fee0f477d9ef9fd52fd3e6a0b436055ac9b25c3