On systemd system, at least CentOS 7, `service foo start` command
works as wrapper of `systemctl start foo`. However, xrdp installs
init script into /etc/init.d/xrdp. This script is not necessary
for systemd system, and, what is worse, if init.d/xrdp exists,
`service xrdp start` works as wrapper to run init.d/xrdp. Maybe
this is inconvinient for many users.