database/sql: boostrap mysql on Red Hat / CentOS

Before starting the Galera cluster, we need to manually bootstrap MySQL
database.
It was done in MariaDB packages, but now for Red Hat, we don't use
anymore MariaDB repository.

This patch installs MySQL database and notify the bootstrap.

Closes-bug #567
Merge pull request #568 from enovance/issue/567/emilien

database/sql: boostrap mysql on Red Hat / CentOS