sctp.Read sometimes returns DeadlineExceededError on past cancelled deadlines

[sukunrt]

Your environment.

• Version: 1.8.7
• Browser: NA
• Other Information:
  We use pion/webrtc in go-libp2p for providing go nodes connectivity with browser libp2p nodes. In our testing environment we've observed some incorrect DeadlineExceededErrors from previous calls to SetReadDeadline after we had updated the Read deadline.
  The fix in check if deadline timer has been cancelled before signaling #290 ensures that any past deadline timer expiry that happens after SetReadDeadline returns is ignored.

What did you do?

Called SetReadDeadline multiple times

What did you expect?

After the last call to SetReadDeadline previous deadline timers should have been ignored

What happened?

Every once a while we observe a past deadline timer firing

[sukunrt]

fixed by #290