OPTIM: epoll: current fd does not count as a new one

OPTIM: epoll: current fd does not count as a new one

The epoll loop checks for newly appeared FDs in order to process them early
if they're accepted sockets. Since the introduction of the fd_ev_set()
calls before the iocb(), the current FD is always in the update list,
and we don't want to check it again, so we must assign the old_updt
index just before calling the I/O handler.