use default if request port is 0.

lichao

2021-06-01 7c8e2433992aac41bdeb0d7d0861b738d9866628

 src/shm.cpp

@@ -25,6 +25,7 @@
    mshm_t(open_or_create, name.c_str(), size, 0, AllowAll()),
    name_(name)
{
   pmutex_ = FindOrCreate<Mutex>("ShmSelfControlMutex0");
}

SharedMemory::~SharedMemory()