infinite loop in write_all when closing socket

[Osso]

In packet.py, line 236, the function write_all loops on len(out).

On my laptop, when asking for a tunnel close (thus closing the socket)
while write_all is running, we can reach a situation where:
* n = self.__socket.send(out) sets n = 0
* socket.send is not sending a socket error even if the socket is closed
This step seems to be limited to mac os 10.5 as I haven't been able to reproduce it on linux
* self.__closed is only tested on socket timeout or error

I thereby suggest to change the test:
"if got timeout" at line 255 to "if got_timeout or self.__closed:" to test each time for a closed socket.