routing: refactor update id logging

Increment update id only on update receival instead of
each loop cycle which results in odd update id values due to second select case branch.

Follow up on #3112

Signed-off-by: Alexander Yastrebov <alexander.yastrebov@zalando.de>

routing/datasource.go

@@ -542,14 +542,16 @@ func receiveRouteMatcher(o Options, out chan<- *routeTable, quit <-chan struct{}
 		rt           *routeTable
 		outRelay     chan<- *routeTable
 		updatesRelay <-chan []*eskip.Route
+		updateId     int
 	)
 	updatesRelay = updates
-	for id := 1; ; id++ {
+	for {
 		select {
 		case defs := <-updatesRelay:
+			updateId++
 			start := time.Now()
 
-			o.Log.Infof("route settings received, id: %d", id)
+			o.Log.Infof("route settings received, id: %d", updateId)
 
 			for i := range o.PreProcessors {
 				defs = o.PreProcessors[i].Do(defs)
@@ -585,7 +587,7 @@ func receiveRouteMatcher(o Options, out chan<- *routeTable, quit <-chan struct{}
 			})
 
 			rt = &routeTable{
-				id:            id,
+				id:            updateId,
 				m:             m,
 				routes:        routes,
 				validRoutes:   validRoutes,