[qemu vm] removed unnecessary condition variable notification since w…

…e use vm_process->wait_for_finished to sync

src/platform/backends/qemu/qemu_virtual_machine.cpp

@@ -469,8 +469,6 @@ void mp::QemuVirtualMachine::on_shutdown()
         vm_process.reset(nullptr);
     }
 
-    state_wait.notify_all();
-
     monitor->on_shutdown();
 }