Adding combined workers in the global scheduling context.

src/core/combined_workers.c

@@ -160,6 +160,8 @@ int starpu_combined_worker_assign_workerid(int nworkers, int workerid_array[])
 #endif
 	}
 
+	starpu_sched_ctx_add_workers(&combined_worker_id, 1, STARPU_GLOBAL_SCHED_CTX);
+
 	return new_workerid;
 }