Add Oak build group to R51 release waterfall

BUG=None
TEST=None

Change-Id: Ic20644a8a5234acd703f656fee24831d5af7bfcf
Reviewed-on: https://chromium-review.googlesource.com/341040
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
Commit-Queue: Bernie Thompson <bhthompson@chromium.org>
Tested-by: Bernie Thompson <bhthompson@chromium.org>
3 files changed