package_manager.py: fixes for multilib deb packaging builds

package_manager.py: fixes for multilib deb packaging builds

* tmp/deploy/deb subdirectories do not get hyphens replaced
  with underscores, so don't do that translation when building
  the sources list.

* Fix MULTILIB_VARIANTS handling to be more general and
  work for all architectures

* Also include a fix for a warning generated by apt
  due to missing apt/preferences.d directory.

(From OE-Core rev: c3ee9b12ae704eadf02ff288d8035b5885d6218e)

Signed-off-by: Matt Madison <matt@madison.systems>
Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>