Another circular symlink in 3.0-2: cont-usr.tex

[Julian Gilbey <jdg@polya.uklinux.net>]

I got another circular symlink issue upgrading from 2.0.2-something to
3.0-2: /etc/texmf/context/cont-usr.tex

I presume it's because
/usr/share/texmf/tex/context/config/cont-usr.tex is a symlink to
/etc/texmf/context/cont-usr.tex but
/usr/share/texmf/tex/context/config used to be a symlink to
/etc/texmf/context
and therefore is the same as bug #297614.

   Julian