use UNAVAILABLE if CDS resource is not okay

src/core/ext/filters/gcp_authentication/gcp_authentication_filter.cc

@@ -75,7 +75,7 @@ absl::Status GcpAuthenticationFilter::Call::OnClientInitialMetadata(
     // because once that happens, a new instance of this filter will be
     // swapped in for subsequent calls, but *this* call is already tied
     // to this filter instance, which will never see the update.
-    return absl::UnauthenticatedError(
+    return absl::UnavailableError(
         absl::StrCat("GCP authentication filter: CDS resource unavailable for ",
                      cluster_name));
   }

test/core/filters/gcp_authentication_filter_test.cc

@@ -249,7 +249,7 @@ TEST_F(GcpAuthenticationFilterTest, FailsCallIfClusterNotOkayInXdsConfig) {
   service_config_call_data->SetCallAttribute(&xds_cluster_attribute);
   call.Start(call.NewClientMetadata());
   EXPECT_EVENT(Finished(
-      &call, HasMetadataResult(absl::UnauthenticatedError(absl::StrCat(
+      &call, HasMetadataResult(absl::UnavailableError(absl::StrCat(
                  "GCP authentication filter: CDS resource unavailable for ",
                  kClusterName)))));
   Step();