Fix typo in autoroll code.
Fix typo in autoroll code.

Introduced in a1a47c8bf997d1f069a3ee088ffa7303a1f8a7cb.

Needs more tests :)

TBR=d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org

Bug: 850351
Change-Id: Ib63a705c2210b7b2d605cf0f8eafbb7d80509f81
Reviewed-on: https://chromium-review.googlesource.com/1110937
Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Reviewed-by: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>
Reviewed-by: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>
Commit-Queue: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>

luci/recipes-py,luci/recipes-py