dot.profile: handle symlinked $HOME

Reapply 4cea05a273c875b5d5d4c41bfa6f2f0a60fa4a66:

Make sh(1) recognize the default $HOME.  By default /home
is a symlink; without this change, when you log in, sh(1)
won't realize the current directory (eg '/usr/home/test')
is the same as $HOME ('/home/test').

/home is no longer a symlink by default, but new users may be added on
systems that started out with an earlier version of FreeBSD (and still
have /home as a symlink) or admins may do so.

This test is not particularly expensive, so just restore it.

Suggested by: danfe, brooks