tailscaled: fix systemd unit definition.

Port number has to be by itself for substitution to work.

Disabling the restart rate-limiting has to be in [Unit] not
[Service].

Signed-off-by: David Anderson <dave@natulte.net>

cmd/tailscaled/tailscaled.service

@@ -3,13 +3,14 @@ Description=Tailscale node agent
 Documentation=https://tailscale.com/kb/
 Wants=network-pre.target
 After=network-pre.target
+StartLimitIntervalSec=0
+StartLimitBurst=0
 
 [Service]
 EnvironmentFile=/etc/default/tailscaled
-ExecStart=/usr/sbin/tailscaled --state=/var/lib/tailscale/tailscaled.state --socket=/run/tailscale/tailscaled.sock --port=$PORT $FLAGS
+ExecStart=/usr/sbin/tailscaled --state=/var/lib/tailscale/tailscaled.state --socket=/run/tailscale/tailscaled.sock --port $PORT $FLAGS
 
 Restart=on-failure
-StartLimitIntervalSec=0
 
 RuntimeDirectory=tailscale
 RuntimeDirectoryMode=0755