ipc tests: Clean up qlocalsocket correctly.

If we don't do this, on_error will be invoked with old sockets, when
self._socket is None...

tests/unit/misc/test_ipc.py

@@ -59,13 +59,15 @@ def qlocalserver(qapp):
 
 
 @pytest.yield_fixture
-def qlocalsocket(qapp):
+def qlocalsocket(qapp, qtbot):
     socket = QLocalSocket()
     yield socket
     socket.disconnectFromServer()
     if socket.state() != QLocalSocket.UnconnectedState:
         disconnected = socket.waitForDisconnected(100)
         assert disconnected
+    with qtbot.waitSignal(socket.destroyed, raising=False):
+        socket.deleteLater()
 
 
 class FakeSocket(QObject):