Fix dependency issues introduced with anchor.

Fix dependency issues introduced with anchor.

apt::ppa and apt::builddep requires apt class. The anchor introduced for
containment of apt-get update causes a dependency loop. apt::ppa appears
to depend on apt class sources.d direcory. While apt::builddep have no
clear reason for a dependency on apt class. This change refactor both
define type, so they no longer cause a dependency loop.