MFC r202500:

MFC r202500:

  Fix a regression that was introduced in r191882.

  I changed login_tty() to only work when the application is not a session
  leader yet. This works fine for applications in the base system, but it
  turns out various applications call this function after daemonizing,
  which means they already use their own session.

  If setsid() fails, just call tcsetsid() on the current session.
  tcsetsid() will already perform proper security checks.

Reported by:	Oliver Lehmann

git-svn-id: svn://svn.freebsd.org/base/stable/8@202929 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f