[task scheduler] Logging to diagnose idle Nexus6p bots.
[task scheduler] Logging to diagnose idle Nexus6p bots.

BUG=skia:

Change-Id: I47c1381285818fcdaf74dc08bda9a81062ebfa71
Reviewed-on: https://skia-review.googlesource.com/5102
Commit-Queue: Ben Wagner <3ef7217be91069877d94f7907ce5479000772cd3@google.com>
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@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