xds: routing policy should immediately update a picker that selects base on updated config (backport v1.31.x) (#7233) (#7241)

The routing LB policy should immediately the Channel's picker that delegates picking to the updated routes. Otherwise, new RPCs will keep being sent through old routes even if they are removed. This change also includes the fix for syncing state change for child balancers in deactivated state.

Author: voidzcy

xds/src/main/java/io/grpc/xds/XdsRoutingLoadBalancer.java

@@ -86,14 +86,14 @@ public void handleResolvedAddresses(final ResolvedAddresses resolvedAddresses) {
       } else {
         childLbStates.get(actionName).reactivate(action.getProvider());
       }
+      final LoadBalancer childLb = childLbStates.get(actionName).lb;
       syncContext.execute(new Runnable() {
         @Override
         public void run() {
-          childLbStates.get(actionName).lb
-              .handleResolvedAddresses(
-                  resolvedAddresses.toBuilder()
-                      .setLoadBalancingPolicyConfig(action.getConfig())
-                      .build());
+          childLb.handleResolvedAddresses(
+              resolvedAddresses.toBuilder()
+                  .setLoadBalancingPolicyConfig(action.getConfig())
+                  .build());
         }
       });
     }
@@ -102,6 +102,7 @@ public void run() {
     for (String actionName : diff) {
       childLbStates.get(actionName).deactivate();
     }
+    updateOverallBalancingState();
   }
 
   @Override
@@ -235,12 +236,11 @@ private final class RouteHelper extends ForwardingLoadBalancerHelper {
 
       @Override
       public void updateBalancingState(ConnectivityState newState, SubchannelPicker newPicker) {
-        if (deactivated) {
-          return;
-        }
         currentState = newState;
         currentPicker = newPicker;
-        updateOverallBalancingState();
+        if (!deactivated) {
+          updateOverallBalancingState();
+        }
       }
 
       @Override