clean up systemd .service files

hddemux.service

 [Unit]
 Description=HTTP/DNS demuxer service
 Documentation=man:hddemux(1)
-## This is a socket-activated service:
-RefuseManualStart=true
+Requires=hddemux.socket
 
 [Service]
 Type=notify
 ExecStart=/usr/bin/hddemux
 WorkingDirectory=/run/hddemux/workdir
+User=hddemux
+Group=hddemux
 
 [Install]
-WantedBy=sockets.target
+Also=hddemux.socket

hddemux.socket

 [Unit]
 Description=HTTP/DNS demuxer socket
 Documentation=man:hddemux(1)
-Before=sockets.target
 
 [Socket]
 ListenStream=/run/hddemux/socket