api: When forwarding from Listener onAddresses to Listener2 continue to use onResult (grpc#11666)

When forwarding from Listener onAddresses to Listener2 continue to use onResult and not onResult2 because the latter requires to be called from within synchronization context and it breaks existing code that didn't need to do so when using the old Listener interface.

Author: kannanjgithub

api/src/main/java/io/grpc/NameResolver.java

@@ -219,13 +219,15 @@ public abstract static class Listener2 implements Listener {
     @Override
     @Deprecated
     @InlineMe(
-        replacement = "this.onResult2(ResolutionResult.newBuilder().setAddressesOrError("
+        replacement = "this.onResult(ResolutionResult.newBuilder().setAddressesOrError("
             + "StatusOr.fromValue(servers)).setAttributes(attributes).build())",
         imports = {"io.grpc.NameResolver.ResolutionResult", "io.grpc.StatusOr"})
     public final void onAddresses(
         List<EquivalentAddressGroup> servers, @ResolutionResultAttr Attributes attributes) {
       // TODO(jihuncho) need to promote Listener2 if we want to use ConfigOrError
-      onResult2(
+      // Calling onResult and not onResult2 because onResult2 can only be called from a
+      // synchronization context.
+      onResult(
           ResolutionResult.newBuilder().setAddressesOrError(
               StatusOr.fromValue(servers)).setAttributes(attributes).build());
     }