windows: do not close stdout on flush() failure

It's been there since 84af5a079c7d (2007-02-19), but seems wrong since any
I/O operations to a closed file would raise ValueError, not IOError. We should
keep the file object open even if the underlying file descriptor is half dead.

mercurial/windows.py

@@ -180,7 +180,6 @@ class winstdout(object):
         except IOError as inst:
             if inst.errno != errno.EINVAL:
                 raise
-            self.close()
             raise IOError(errno.EPIPE, 'Broken pipe')
 
 def _is_win_9x():