Fixed AllServerUnavailableFailFast test to return UNAVAILBLE instead

UNKNOWN.

src/core/ext/filters/client_channel/lb_policy/xds/xds_routing.cc

@@ -393,8 +393,8 @@ void XdsRoutingLb::UpdateStateLocked() {
       break;
     default:
       picker = absl::make_unique<TransientFailurePicker>(
-          GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-              "xds_routing: all children report state TRANSIENT_FAILURE"));
+          grpc_error_set_int(GRPC_ERROR_CREATE_FROM_STATIC_STRING("TRANSIENT_FAILURE from XdsRoutingLb"),
+                           GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_UNAVAILABLE));
   }
   channel_control_helper()->UpdateState(connectivity_state, std::move(picker));
 }

test/cpp/end2end/xds_end2end_test.cc

@@ -1748,9 +1748,7 @@ TEST_P(BasicTest, AllServersUnreachableFailFast) {
       AdsServiceImpl::BuildEdsResource(args), kDefaultResourceName);
   const Status status = SendRpc();
   // The error shouldn't be DEADLINE_EXCEEDED.
-  gpr_log(GPR_INFO, "error code %d message received %s", status.error_code(),
-          status.error_message().c_str());
-  EXPECT_NE(StatusCode::DEADLINE_EXCEEDED, status.error_code());
+  EXPECT_EQ(StatusCode::UNAVAILABLE, status.error_code());
 }
 
 // Tests that RPCs fail when the backends are down, and will succeed again after