Remove mariadb-server package during installation

If mariadb-server is installed, it will conflict with requested
package mariadb-galera-server, and installation will fail. This
patch fixes that by making sure mariadb-server is uninstalled
befora mariadb-galera-server installation is attempted.

Change-Id: Iebc703b778626223fe2f5875304df9cdc874cabe
Fixes: bz#1148578
Merge "Remove mariadb-server package during installation"