backout dc68fcf06253e8844f8803f7f5a144c46a274615
bug 851278 - exclude test stub apps from dogfood builds
(cherry picked from commit 73f407d356db424dd689543a6cacee5b36861a42)

bug 851278 followup - remove obsolete dir from external apps dirs
(cherry picked from commit fc6fa694cbe2ac792db1fb756824228c1b6682be)