Revert part of 4374: a test explicitly needs EINVAL being returned.

mpi/starpu_mpi_insert_task.c

@@ -234,7 +234,8 @@ int starpu_mpi_insert_task(MPI_Comm comm, starpu_codelet *codelet, ...)
 
         if (inconsistent_execute == 1) {
                 if (execute == -1) {
-                        _STARPU_ERROR("Different tasks are owning W data. Needs to specify which one is to execute the codelet, using STARPU_EXECUTE_ON_NODE or STARPU_EXECUTE_ON_DATA\n");
+                        _STARPU_MPI_DEBUG("Different tasks are owning W data. Needs to specify which one is to execute the codelet, using STARPU_EXECUTE_ON_NODE or STARPU_EXECUTE_ON_DATA\n");
+			return -EINVAL;
                 }
                 else {
                         do_execute = (me == execute);