Revert "agent: refactor sync loop to linear flow of control"

This reverts commit 7a2af206ea.

agent/ae/ae.go

@@ -93,10 +93,12 @@ func (s *StateSyncer) Run() {
 
 Sync:
 	for {
-		switch err := s.State.UpdateSyncState(); {
+		// update the sync status
+		err := s.State.UpdateSyncState()
+		if err == nil {
+			break
+		}
 
-		// update sync status failed
-		case err != nil:
 		s.Logger.Printf("[ERR] agent: failed to sync remote state: %v", err)
 
 		// retry updating sync status after some time or when a consul
@@ -104,7 +106,7 @@ Sync:
 		select {
 
 		// consul server added to cluster.
-			// retry sooner than retryFailIntv to converge cluster sooner
+		// retry sooner than retryFailIntv to converge cluster quicker
 		// but stagger delay to avoid thundering herd
 		case <-s.ServerUpCh:
 			select {
@@ -120,13 +122,12 @@ Sync:
 		case <-s.ShutdownCh:
 			return
 		}
+	}
 
-		// update sync status OK
-		default:
-			// force-trigger sync to pickup any changes
+	// Force-trigger sync to pickup any changes
 	s.triggerSync()
 
-			// do partial syncs until it is time for a full sync again
+	// Wait for sync events
 	for {
 		select {
 		// todo(fs): why don't we honor the ServerUpCh here as well?
@@ -140,7 +141,7 @@ Sync:
 		// 	}
 
 		case <-time.After(s.Interval + stagger(s.Interval)):
-					continue Sync
+			goto Sync
 
 		case <-s.TriggerCh:
 			if s.Paused() {
@@ -155,8 +156,6 @@ Sync:
 		}
 	}
 }
-	}
-}
 
 // Pause temporarily disables sync runs.
 func (s *StateSyncer) Pause() {