which_conf_file

we should not return the path, but just set the Cnf values to whatever is
in that local config file, so that can point to the right dak.conf then.
and, as that will be different from default "/etc/dak/dak.conf" then let
the usual process read in our different config files

Signed-off-by: Joerg Jaspert <joerg@debian.org>