MP1-2803 : Fix possibility to reinstall MySQL 5.6 if we manually uninstall MySQL 5.1 and 5.6 when select 'Reinstall Current MP version' in DeployTool.
This mean : if user uninstall MySQL 5.1 (should be auto uninstalled on upgrade but sometimes the uninstall didn't go) it will uninstall MySQL 5.6 and then MySQL is not working anymore.
To fix it, user need to uninstall MySQL 5.6 (Database is kept) and start MP installer and select option 'Reinstall Current MP version'.
It will reinstall MySQL 5.6 and used user database.