Change MariaDB repo from JMU to OSU

This patch changes the MariaDB repository used from JMU to OSU, which
appears to be the primary source repository for all mirrors.

This has become necessary due to JMU's mirror being unavailable due to
maintenance.

Change-Id: I5b42c85bf87b4032334177f7411fb4527860a19f
Closes-Bug: #1403795
(cherry picked from commit ae07f1a08cb56d98a8d5043db9b71569532970bc)