Negate 'none' check condition for FLAGS_call_creds

Bug: 261533497
Test: pass --call_creds=none, and there is no warning msg.
Change-Id: If8585de60aa1784c8e19a5e2d73acaf279295d9b
diff --git a/test/cpp/util/cli_credentials.cc b/test/cpp/util/cli_credentials.cc
index 1125b2d..91acc90 100644
--- a/test/cpp/util/cli_credentials.cc
+++ b/test/cpp/util/cli_credentials.cc
@@ -151,7 +151,7 @@
   if (IsAccessToken(FLAGS_call_creds)) {
     return grpc::AccessTokenCredentials(AccessToken(FLAGS_call_creds));
   }
-  if (FLAGS_call_creds.compare("none") != 0) {
+  if (FLAGS_call_creds.compare("none") == 0) {
     // Nothing to do; creds, if any, are baked into the channel.
     return std::shared_ptr<grpc::CallCredentials>();
   }