Fix race condition when setting m_DirectWork by NOT assuming that pthread_cond_broadcast necessarily involves that the next thread to acquire the mutex is the the one blocked on pthread_cond_wait but rather take into account that another thread could get in and re-assign m_DirectWork resulting into a lost task and a hanged erlang process:
    {current_stacktrace,[{eleveldb,write,3, [{file,"src/eleveldb.erl"},{line,150}]}