[autorollers] Cleanup checkout after abandoning repo branch
[autorollers] Cleanup checkout after abandoning repo branch

Bug: skia:12789
Change-Id: I8b07a6f8b9c0a499d5144b96fba7ea7471285438
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/492025
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@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