Merge pull request #559 from tufang14/2.0release

srs reusable thread need join

@@ -232,11 +232,6 @@ namespace internal {
         // readly terminated now.
         really_terminated = true;
         
-        // when thread terminated normally, also disposed.
-        // we must set to disposed before the on_thread_stop, which may free the thread.
-        // @see https://github.com/ossrs/srs/issues/546
-        disposed = true;
-        
         handler->on_thread_stop();
         srs_info("thread %s cycle finished", _name);
     }