Add Databases backup to CentOS script
Add Databases backup to CentOS script

To fix https://github.com/SeafileDE/seafile-server-installer/issues/79

syncwerk/syncwerk-server-installer,shoeper/seafile-server-installer,haiwen/seafile-server-installer,felag/seafile-server-installer,seafile/seafile-server-installer,SeafileDE/seafile-server-installer