Proton transport objects leaked if client disconnects abruptly leading to OutOfMemoryError: Java heap space

https://issues.apache.org/jira/browse/ARTEMIS-2002

If an AMQP client with an attached receiving link disconnects abruptly (i.e. closes socket without sending the AMQP close performative), TransportImpl and other Proton class instances remain referenced within the heap. If many such clients do this, an OutOfMemoryError: Java heap space occurs. This occurs even though the underlying socket connection has been closed.

I have reproduced this issue against Artemis upstream (both 2.6.2 and master (f0c13622ac7e821a81a354b0242ef5235b6e82df)).