check if clientSettingsEndpoint is default endpoint

Author: rmehta19

gax-java/gax/src/main/java/com/google/api/gax/rpc/EndpointContext.java

@@ -327,7 +327,9 @@ boolean shouldUseS2A() {
       }
 
       // If a custom endpoint is being used, skip S2A.
-      if (!Strings.isNullOrEmpty(clientSettingsEndpoint())
+      if ((!Strings.isNullOrEmpty(clientSettingsEndpoint())
+              && !buildEndpointTemplate(serviceName(), resolvedUniverseDomain())
+                  .contains(clientSettingsEndpoint()))
           || (!Strings.isNullOrEmpty(transportChannelProviderEndpoint())
               && !buildEndpointTemplate(serviceName(), resolvedUniverseDomain())
                   .contains(transportChannelProviderEndpoint()))) {