Close transport on broker server disconnect

[kkocdko]

Fixed #110

[julian-graf]

Thanks for the PR. The CI failure is weird, especially because it seems to be related to a test you haven't modified. I'll check out what is happening here.

[julian-graf]

Alright, I figured out the issue. HiveMQ responds with a DISCONNECT on keep alive timeout which leads to an MqttError::Disconnect followed by MqttError::RecoveryRequired's. This leads to the break pattern in the test never matching. Additionally, the tokio::timeout never fires either because the loop turns into a hot loop not reaching a single await point once this error has occured. Mosquitto just closes the connection so an MqttError::Network is returned. The other tests already check for both conditions not sure why just this one didn't.

Do you want to fix this or should I? In the latter case, I'd add this to the changelog etc. as well.

[kkocdko]

@julian-graf I might be busy these days, feel free to reuse/copy/modify/close this PR :)