Add fedora support

For x86_64, MariaDB 5.5 has a bug in their repo (see: https://mariadb.atlassian.net/browse/MDEV-5152).
Additionally, Fedora packages MariaDB as its default version of "MySQL"
This adds the fedora platform_family in the places that's needed and switches to the system packages.
The system package switch can be undone later when the above bug is fixed, if desired (currently slated for MariaDB 5.6)