Don't break existing connections when using systemd. Closes: #752094

debian/pptpd.service

@@ -6,6 +6,7 @@ After=network.target
 EnvironmentFile=-/etc/default/pptpd
 # don't daemonize to simplify stuff
 ExecStart=/usr/sbin/pptpd --fg $DAEMON_OPTS
+KillMode=process
 
 [Install]
 WantedBy=multi-user.target