change refcount, avoid ShmMsgQueue AddRef on send.

lichao

2021-05-14 c0d61292ef6bdd8e2e93525b5df6a8ec5c017c32

 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()