qml: use daemon threads everywhere the network is involved

The app hangs indefinitely if we try to quit it while one of
these threads is active, because once asyncio has shut down,
futures never return. This was already fixed for lightning
payments in c5dc133, but there are many other cases.

electrum/gui/qml/qechanneldetails.py

@@ -194,7 +194,7 @@ class QEChannelDetails(QObject, QtEventListener):
                 self._logger.exception("Could not close channel: " + repr(e))
                 self.channelCloseFailed.emit(_('Could not close channel: ') + repr(e))
 
-        threading.Thread(target=do_close).start()
+        threading.Thread(target=do_close, daemon=True).start()
 
     @pyqtSlot()
     def deleteChannel(self):