fixed undefined behavior in mutex locks
fixed undefined behavior in mutex locks

uv_mutex_unlock() was invoked by the main thread and not the thread that originally locked the mutex.
mathiask88/node-snap7,JanczuraPiotr/node-snap7,mathiask88/node-snap7,JanczuraPiotr/node-snap7,mathiask88/node-snap7,JanczuraPiotr/node-snap7