Fix MultiTimeout_Destroy test.

tdactor/test/actors_bugs.cpp

@@ -82,6 +82,8 @@ class TimeoutManager : public Actor {
 
   void test_timeout() {
     CHECK(count > 0);
+    // we must yield scheduler, so run_main breaks immediately, if timeouts are handled immediately
+    Scheduler::instance()->yield();
   }
 
   MultiTimeout test_timeout_{"TestTimeout"};