Commit 27d23b1d has changed the convention that scripts with Sxxx
symlinks should be run with "stop" parameter in runlevels 0 and 6.
They should now be called with the more intuitive "start" parameter.
But a few scripts still call "/etc/init.d/halt stop". Fortunately, this
occurs in code paths that are rarely run (unrecoverable errors). So it
was not noticed until now. Anyway, this is fixed in this commit.