Cygwin: pty: Disable FreeConsole() on close for non cygwin process.

Cygwin: pty: Disable FreeConsole() on close for non cygwin process.

- After commit e1a0775dc0545b5f9c81b09a327fc110c538b7b4, the problem
  reported in https://www.cygwin.com/ml/cygwin/2020-01/msg00093.html
  occurs. For Gnu scren and tmux, calling FreeConsole() on pty close
  is necessary. However, if FreeConsole() is called, cygwin setup
  with '-h' option does not work. Therefore, the commit
  e1a0775dc0545b5f9c81b09a327fc110c538b7b4 delayed closing pty.
  This is the cause of the problem above. Now, instead of delaying
  pty close, FreeConsole() is not called if the process is non cygwin
  processes such as cygwin setup.