In some circumstances, particularly with 'opportunistic_writes' and
'fatal_errors' enabled in the epoll backend, the connection may be closed
halfway through the session close process (because it contains debug logging,
which in the case of the watch:log() command, will trigger a write to the
socket).
The chosen fix is to cache session.conn in a local variable (we already did
this later on, but this pulls it up to the top of the function, which is
generally more correct anyway).
The "socket.unix" module exported only a function before
aa1b8cc9bc
when datagram support was added.
Fixes#1717
Thanks rsc and lucas for reporting and testing
This may in theory cause multiple disconnect events for the
adminstream client, if the only code using that wasn't calling
os.exit right away.
Hence, this should be a good enough partial fix for #1671. It is
not a full fix, because the shell will only notice the disconnect
after one has hit enter in the input; until then, it is stuck in
a read() call to stdin and completely oblivious to the disconnect.
