Fix bug in ProcessGDBRemote

[labath]

Summary

ProcessGDBRemote::AsyncThread nuked its own thread handle upon exiting. This prevented the main
thread from joining it correctly in StopAsyncThread. I address this by moving the Reset() call to
StopAsyncThread, after the join.

source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

ProcessGDBRemote::StopAsyncThread ()
     {
         m_async_broadcaster.BroadcastEvent (eBroadcastBitAsyncThreadShouldExit);
         
         //  This will shut down the async thread.
         m_gdb_comm.Disconnect();    // Disconnect from the debug server.
 
         // Stop the stdio thread
         m_async_thread.Join(nullptr);
+        m_async_thread.Reset();
     }
     else if (log)
         log->Printf("ProcessGDBRemote::%s () - Called when Async thread was not running.", __FUNCTION__);
 }
 
 
 thread_result_t
 ProcessGDBRemote::AsyncThread (void *arg)
if (listener.StartListeningForEvents (&process->m_async_broadcaster, desired_event_mask) == desired_event_mask)
                 done = true;
             }
         }
     }
 
     if (log)
         log->Printf ("ProcessGDBRemote::%s (arg = %p, pid = %" PRIu64 ") thread exiting...", __FUNCTION__, arg, process->GetID());
 
-    process->m_async_thread.Reset();
     return NULL;
 }
 
 //uint32_t
 //ProcessGDBRemote::ListProcessesMatchingName (const char *name, StringList &matches, std::vector<lldb::pid_t> &pids)
 //{
 //    // If we are planning to launch the debugserver remotely, then we need to fire up a debugserver
 //    // process and ask it for the list of processes. But if we are local, we can let the Host do it.