TT#26264 Add a new systemd native service file

This service file assumes that the new mediator configuration is in
place to define all the options to use.

Change-Id: I876a0764f3355dd040baf4824794483ec734e2f3

debian/ngcp-mediator.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=NGCP Mediator
+Requires=mysql.service
+After=remote-fs.target
+After=mysql.service
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/mediator
+
+[Install]
+WantedBy=multi-user.target
+Alias=mediator.service