Support specifying hash and patch_ref in docker/Dockerfile
Support specifying hash and patch_ref in docker/Dockerfile

This docker file should not be checking out ToT code.

Bug: skia:10198
Change-Id: I531b9344da9c972d64a974c73f38af5477cf15a8
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/286537
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