Reserve pipe in step names.
Reserve pipe in step names.

Bug: 742478
Change-Id: I2d15a1d78f887f7ba9916601874e2afe3537f2e8
Reviewed-on: https://chromium-review.googlesource.com/947051
Commit-Queue: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>

luci/recipes-py,luci/recipes-py