test: remove CONSTRUCT_ON_FIRST_USE from ads_integration_test (envoyp…

…roxy#8272)

This string constant is not constant when ads_integration_test is parameterized on delta/SotW.

Risk Level: none
Testing: test-only change
Doc Changes: n /a
Release Notes:  n/a

Signed-off-by: Fred Douglas <fredlas@google.com>

test/integration/ads_integration.h

@@ -13,8 +13,9 @@
 #include "test/integration/http_integration.h"
 
 namespace Envoy {
-static const std::string& AdsIntegrationConfig() {
-  CONSTRUCT_ON_FIRST_USE(std::string, R"EOF(
+static std::string AdsIntegrationConfig() {
+  // Note: do not use CONSTRUCT_ON_FIRST_USE here!
+  return R"EOF(
 dynamic_resources:
   lds_config: {ads: {}}
   cds_config: {ads: {}}
@@ -38,7 +39,7 @@ static const std::string& AdsIntegrationConfig() {
     socket_address:
       address: 127.0.0.1
       port_value: 0
-)EOF");
+)EOF";
 }
 
 class AdsIntegrationTest : public Grpc::GrpcClientIntegrationParamTest, public HttpIntegrationTest {