Fix a socket leak: delete object after close on both direction.

(Note by apenwarr: seems to still work for me.  The reason the
problem occurred is that reassigning 'handlers' doesn't change it in its
parent; it creates a whole new list, and the caller still owns the old one
with all the dead sockets in it.  The problem seems to have been introduced
in commit 84376284db6199d4928797e5e8be4182449120f2 when I factored the
runonce() functionality out of the client and server but didn't notice this
reassignment.)

ssnet.py

@@ -468,7 +468,10 @@ def runonce(handlers, mux):
     r = []
     w = []
     x = []
-    handlers = filter(lambda s: s.ok, handlers)
+    to_remove = filter(lambda s: not s.ok, handlers)
+    for h in to_remove:
+        handlers.remove(h)
+
     for s in handlers:
         s.pre_select(r,w,x)
     debug2('Waiting: %d r=%r w=%r x=%r (fullness=%d/%d)\n'