Revert "Default to MariaDB for SLES 12"

SLES belongs in the Suse family, not the RedHat family.

This reverts commit 8cc0083d6e58b21328504d8de9c02a497dd93a11.
Add support for SLES 12

SLES 12 has different package names for the server and client. It also
doesn't seem to want to start if basedir is defined.
Merge pull request #610 from cmurphy/sles12

Fix support for SLES 12