Update android-skqp Docker image to accept licenses

Set DOCKER_CONFIG env var for all docker commands so that the Swarming
task uses the config created here:
https://skia.googlesource.com/buildbot/+/06aaf21b5d91a68de7c02aafc0fdee8531ba0c21/scripts/run_on_swarming_bots/install_docker.py#65

Bug: skia:8698
Change-Id: I731a99abc274caa498af8dde5142a7e6a6b6eca3
Reviewed-on: https://skia-review.googlesource.com/c/185690
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
Reviewed-by: Stephan Altmueller <stephana@google.com>
31 files changed