HMI disconnects from the backend server after a failed HMI PTU

[ShobhitAd]

Bug Report

Generic HMI disconnects from the backend server on a failed HMI PTU. As a result other backend related features (video/audio streaming, webengine apps) cannot be used after a failed HMI PTU

Reproduction Steps

1. Start backend server and SDL
2. Start Generic HMI
3. Check the "PTU using in-vehicle modem" checkbox
4. Register Test suite app with app type "NAVIGATION"
5. Run Streaming Tests > PlayVideo (RAW) from tests drawer

Expected Behavior

1. The HMI PTU triggered on app registration fails and HMI switches to PTU over mobile
2. Video stream starts in HMI

Observed Behavior

1. The HMI PTU triggered on app registration fails and HMI switches to PTU over mobile. The following error appears in the backend server logs

Traceback (most recent call last):
  File "./python_websocket/src/websockets/server.py", line 193, in handler
    await self.ws_handler(self, path)
  File "./python_websocket/src/start_server.py", line 157, in on_connect
    async for message in _websocket:
  File "./python_websocket/src/websockets/protocol.py", line 437, in __aiter__
    yield await self.recv()
  File "./python_websocket/src/websockets/protocol.py", line 507, in recv
    await self.ensure_open()
  File "./python_websocket/src/websockets/protocol.py", line 810, in ensure_open
    raise self.connection_closed_exc()
websockets.exceptions.ConnectionClosedError: code = 1005 (no status code [internal]), no reason

2. Video stream does NOT start in HMI

Browser & Version Information

• Browser and Version: Chromium (Version 92.0.4515.159)
• Generic HMI Version: develop(76aea6e)
• Testing Against: Test Suite

[ShobhitAd]

Closed via #432