Clear thread task queues on exit

We need to release any shared pointers in the closures.

This solves potentially destroying clients later than intended, when the
thread data is destroyed in the main thread on exit, after the threads
are gone already.

Author: halfgaar

threaddata.cpp

@@ -846,6 +846,10 @@ void ThreadData::acceptPendingBridges()
 
 void ThreadData::deleteClients()
 {
+    // Can have shared pointers to clients
+    taskQueue.lock()->clear();
+    delayedTasks.clear();
+
     clients.by_fd.clear();
     clients.bridges.clear();
     acceptQueue.clients.lock()->clear();