[task scheduler] Reduce warnings about blacklisted candidates into one line per rule
[task scheduler] Reduce warnings about blacklisted candidates into one line per rule

Change-Id: I7c4538931e7301afbe4fbcdea666f74f9d8ff3a5
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/226523
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Reviewed-by: Ben Wagner aka dogben <3ef7217be91069877d94f7907ce5479000772cd3@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