[#108] cmd/neofs-node: Listen new epoch notifications from morph

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

cmd/neofs-node/worker.go

@@ -8,6 +8,20 @@ type worker interface {
 	Run(context.Context)
 }
 
+type workerFromFunc struct {
+	fn func(context.Context)
+}
+
+func newWorkerFromFunc(fn func(ctx context.Context)) worker {
+	return &workerFromFunc{
+		fn: fn,
+	}
+}
+
+func (w *workerFromFunc) Run(ctx context.Context) {
+	w.fn(ctx)
+}
+
 func startWorkers(c *cfg) {
 	for _, wrk := range c.workers {
 		c.wg.Add(1)