Fix echo-pipe.py
Fix echo-pipe.py

$python echo-pipe.py
C-d C-c
Traceback (most recent call last):
  File "pipesrv.py", line 14, in signal_cb
    pipe_stdin.close()
pyuv.error.HandleClosedError: Handle is closing/closed
fivejjs/pyuv,fivejjs/pyuv,fivejjs/pyuv,saghul/pyuv,saghul/pyuv,saghul/pyuv