[CT] Differentiate between Android docker swarming bots and non-docker
[CT] Differentiate between Android docker swarming bots and non-docker

This is the first step to make sure that the not-ready-yet docker Android swarming bots from https://bugs.chromium.org/p/chromium/issues/detail?id=820452 do not pick up any tasks.

Bug: skia:10121
Change-Id: I5db5b62e3f3041a652f3d399be43179556c27d54
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/282362
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@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