add flaky test option

One fuzzer generated pathops test
fails everywhere except for one
builder. Add a flaky state to the
pathops test framework to handle
this until I can investigate
further.

TBR=reed@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2221153005

Review-Url: https://codereview.chromium.org/2221153005
3 files changed