Some people think this upgrade hook gets stuck when in reality, it has
to delete a lot of files (gigs worth). Add some progress messages so
people know it's doing something.
BUG=chromium-os:32052
TEST=manually running 25_suppress_incremental_build_across_chroot showed pretty messages
Change-Id: Ie20980fb2c60c980b617e98d68b0e5f9633fbb2a
Reviewed-on: https://gerrit.chromium.org/gerrit/26111
Reviewed-by: Brian Harring <ferringb@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Ready: Mike Frysinger <vapier@chromium.org>