Potential deadlock in abort

[JoTurk]

Hi, I am currently investigating a peerConnection.Close() that hang forever in some rare case which create a leak and let a lot of buffer taking ram forever

digging deeper into it with pprof, the peerConnection.Close now default to call the association.Abort and it get stuck here: // Wait for readLoop to end <-a.readLoopCloseCh

I am still unable to reproduce the issue manually, and it may take 2 hours of spamming over 20 concurrent webrtc connections for it to happen The association.go use the dtl connection

Do you think it could be related?

Originally posted by @craymond12 in #667

I think it still happens after https://github.com/pion/dtls/pull/709