[gold] Fix test in pdag
[gold] Fix test in pdag

This is not a race condition. Some output wasn't included because
it's rare.

TBR=kjlubick
Bug: skia:7295
Change-Id: I1c90164e1bf18b12162b8e1058d2776531d8fc64
Reviewed-on: https://skia-review.googlesource.com/71501
Reviewed-by: Stephan Altmueller <43343ec95731c0e8daa7359daf7f2f3935582b24@google.com>
Commit-Queue: Stephan Altmueller <43343ec95731c0e8daa7359daf7f2f3935582b24@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