Support dist-ing the userdatatarball

So that we can get to the contents of userdata from the build server
without extracting the image.

Bug: 27719200
Test: m userdatatarball dist
(cherry-picked from 69af2e4102d3af3f5f06e4d7a615d42dbb3446bb)

Change-Id: I1438597bd29df80665571f7dc3b4957b9adde870
1 file changed