Renamed WebRtcTransport webRtcServerClosed() to listenServerClosed()

[piranna]

I've found a typo where the WebRtcTransport.webRtcServerClosed() was never called. Instead, the Transport.listenServerClosed() method is being directly called by WebRtcServer, so the clean-ups done at webRtcServerClosed() are never done. Since listenServerClose event is at Transport level with the idea maybe of have other listener servers in the future (raw TCP? RTP?), I've renamed webRtcServerClosed() to the more generic one listenServerClosed(), calling to the parent class.

[ibc]

And here a new added test that indeed fails in v3 branch and will pass once this PR is merged:

a34ca02

[ibc]

@nazar-pc I am not brave enough to know how this is done in Rust, I couldn't find any similar code so the bug probably doesn't happen in Rust.

[nazar-pc]

Cleanups are done in Drop implementation in Rust, so most likely it works correctly there

[piranna]

And here a new added test that indeed fails in v3 branch and will pass once this PR is merged:

a34ca02

Glad you liked this PR :-)