Fix the compile errors for tests and namespace.

include/grpcpp/security/credentials_impl.h

@@ -44,7 +44,7 @@ class CallCredentials;
 class SecureCallCredentials;
 class SecureChannelCredentials;
 
-std::shared_ptr<grpc::Channel> CreateCustomChannel(
+std::shared_ptr<grpc::Channel> CreateCustomChannelImpl(
     const grpc::string& target,
     const std::shared_ptr<ChannelCredentials>& creds,
     const grpc::ChannelArguments& args);
@@ -78,7 +78,7 @@ class ChannelCredentials : private grpc::GrpcLibraryCodegen {
   virtual SecureChannelCredentials* AsSecureCredentials() = 0;
 
  private:
-  friend std::shared_ptr<grpc::Channel> CreateCustomChannel(
+  friend std::shared_ptr<grpc::Channel> CreateCustomChannelImpl(
       const grpc::string& target,
       const std::shared_ptr<ChannelCredentials>& creds,
       const grpc::ChannelArguments& args);

test/cpp/util/grpc_tool.cc

@@ -217,7 +217,7 @@ std::shared_ptr<grpc::Channel> CreateCliChannel(
   if (!cred.GetSslTargetNameOverride().empty()) {
     args.SetSslTargetNameOverride(cred.GetSslTargetNameOverride());
   }
-  return grpc::CreateCustomChannel(server_address, cred.GetCredentials(), args);
+  return CreateCustomChannel(server_address, cred.GetCredentials(), args);
 }
 
 struct Command {