Bugfix: fixed a deadlock
Bugfix: fixed a deadlock

As of gevent 1.3.6 `gevent.joinall` will deadlock if the same async
result is used twice.

This is a test script to reproduce the problem:

https://gist.github.com/hackaugusto/5baa9a10e5875a00367b4a6f58d24638

hackaugusto/raiden,hackaugusto/raiden