Increase network timeout when checking API key

Some users of OctoPrint 1.5.x report that connecting through the Connect to OctoPrint dialog no longer works because the API is too slow to respond.

Mitigates #211

DiscoverOctoPrintAction.py

@@ -270,7 +270,7 @@ def testApiKey(self, instance_id: str, api_key: str) -> None:
             settings_request.setRawHeader(b"X-Api-Key", api_key.encode())
             self._settings_reply = self._network_manager.get(settings_request)
             self._settings_reply_timeout = NetworkReplyTimeout(
-                self._settings_reply, 5000, self._onRequestFailed
+                self._settings_reply, 20000, self._onRequestFailed
             )
 
             self._settings_instance = instance