[autoroll] Need to update frontend image when pushing a roller
[autoroll] Need to update frontend image when pushing a roller

Since the configs are included in the image, we have to update the
frontend image whenever we push a roller config update.

Change-Id: I5ff53ffc46989583e3cb5a77907410e9c7c99b26
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/487936
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot