willis: move to contrib

Only devs run this directly, so shift it to contrib.

BUG=None
TEST=precq passes
CQ-DEPEND=CL:1278106

Change-Id: I95697ad2f15cf559702d8b6ecfa071bdb2a00a8b
Reviewed-on: https://chromium-review.googlesource.com/1278333
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Alex Klein <saklein@chromium.org>
diff --git a/host/willis b/contrib/willis
similarity index 100%
rename from host/willis
rename to contrib/willis