Remove the now unused $apt_clean variable

Remove the now unused $apt_clean variable

This variable was deprecated in favor of using a list of file sources.
to change the value of the 'clean' property, you can either define a
file '03clean' in a site-apt module, or a per-host '$fqdn/03clean' file
in the same site-apt module.

Also, move the moduledir stuff below nearer to where it's actually used.

Signed-off-by: Gabriel Filion <lelutin@gmail.com>