init: Rename systemd units

Use strongswan-starter for the legacy unit and simply strongswan for the
modern one (strongswan-swanctl is configured as alias, which should
cause the installation of symlinks when the service is enabled via
systemctl).

init/systemd/strongswan.service.in

@@ -1,11 +1,15 @@
 [Unit]
-Description=strongSwan IPsec IKEv1/IKEv2 daemon using ipsec.conf
-After=syslog.target network-online.target
+Description=strongSwan IPsec IKEv1/IKEv2 daemon using swanctl
+After=network-online.target
 
 [Service]
-ExecStart=@SBINDIR@/@IPSEC_SCRIPT@ start --nofork
-StandardOutput=syslog
+Type=notify
+ExecStart=@SBINDIR@/charon-systemd
+ExecStartPost=@SBINDIR@/swanctl --load-all --noprompt
+ExecReload=@SBINDIR@/swanctl --reload
+ExecReload=@SBINDIR@/swanctl --load-all --noprompt
 Restart=on-abnormal
 
 [Install]
 WantedBy=multi-user.target
+Alias=strongswan-swanctl.service