Changed name of rpc method to fit with the conventional naming. Also fixed type in interop client flag help message

src/proto/grpc/testing/test.proto

@@ -77,7 +77,7 @@ service TestService {
 
   // The test server will not implement this method. It will be used
   // to test the behavior when clients call unimplemented methods.
-  rpc UnimplementedMethod(grpc.testing.Empty) returns (grpc.testing.Empty);
+  rpc UnimplementedCall(grpc.testing.Empty) returns (grpc.testing.Empty);
 }
 
 // A simple service NOT implemented at servers so clients can test for

test/cpp/interop/client.cc

@@ -80,7 +80,7 @@ DEFINE_string(test_case, "large_unary",
               "slow client consumer;\n"
               "status_code_and_message: verify status code & message;\n"
               "timeout_on_sleeping_server: deadline exceeds on stream;\n"
-              "unimplemented_method: client calls an unimplemented_method;\n");
+              "unimplemented_method: client calls an unimplemented method;\n");
 DEFINE_string(default_service_account, "",
               "Email of GCE default service account");
 DEFINE_string(service_account_key_file, "",

test/cpp/interop/interop_client.cc

@@ -1010,7 +1010,7 @@ bool InteropClient::DoUnimplementedMethod() {
   ClientContext context;
 
   Status s =
-      serviceStub_.Get()->UnimplementedMethod(&context, request, &response);
+      serviceStub_.Get()->UnimplementedCall(&context, request, &response);
 
   if (!AssertStatusCode(s, StatusCode::UNIMPLEMENTED)) {
     return false;