Fix reconnecting to a camera when it goes offline/online

[szimek]

When camera goes offline and then online again, the listener is not automatically reconnected and sees a black screen, even though it knows that the camera is online again.

[grechut]

This is partially related to the issue of not disconnecting the connection after leaving the device's page while still having watchdog's webapp opened. Not sure whether create a separate issue or create a more general issue about fixes to RTC connection management