cmd: refactor and use sysdnotify in more commands

* cmd: refactor and use sysdnotify in more commands

Fixes #5117

lib/systemd/notify.go

@@ -0,0 +1,32 @@
+package systemd
+
+import (
+	"log"
+	"sync"
+
+	sysdnotify "github.com/iguanesolutions/go-systemd/v5/notify"
+	"github.com/rclone/rclone/lib/atexit"
+)
+
+// Notify systemd that the service is starting. This returns a
+// function which should be called to notify that the service is
+// stopping. This function will be called on exit if the service exits
+// on a signal.
+func Notify() func() {
+	if err := sysdnotify.Ready(); err != nil {
+		log.Printf("failed to notify ready to systemd: %v", err)
+	}
+	var finaliseOnce sync.Once
+	finalise := func() {
+		finaliseOnce.Do(func() {
+			if err := sysdnotify.Stopping(); err != nil {
+				log.Printf("failed to notify stopping to systemd: %v", err)
+			}
+		})
+	}
+	finaliseHandle := atexit.Register(finalise)
+	return func() {
+		atexit.Unregister(finaliseHandle)
+		finalise()
+	}
+}