build: Do not use --deb-systemd with fpm (fixes #7548) (#7564)

script/deb-post-inst.template

@@ -0,0 +1,14 @@
+#!/bin/sh
+
+command -v deb-systemd-invoke > /dev/null
+has_systemd=$?
+
+if [ $has_systemd -eq 0 ]; then
+    systemctl daemon-reload
+fi
+
+if [ $has_systemd -eq 0 ] && [ -n "$(systemctl list-units --plain --no-legend {{.Service}})" ]; then
+    deb-systemd-invoke try-restart "{{.Service}}"
+else
+    pkill -HUP -x {{.Command}}
+fi

script/post-upgrade

@@ -1,8 +0,0 @@
-#!/bin/sh
-
-if command -v deb-systemd-invoke > /dev/null; then
-	deb-systemd-invoke restart procps.service
-else
-	sysctl -q --system
-fi
-pkill -HUP -x syncthing || true