ResumeFromCheckpointStreamingTest flakes with what appears as a second firing.

See: https://builds.apache.org/view/Beam/job/beam_PostCommit_Java_MavenInstall/org.apache.beam$beam-runners-spark/2788/testReport/junit/org.apache.beam.runners.spark.translation.streaming/ResumeFromCheckpointStreamingTest/testWithResume/

After some digging in it appears that a second firing occurs (though only one is expected) but it doesn't come from a stale state (state is empty before it fires).
Might be a retry happening for some reason, which is OK in terms of fault-tolerance guarantees (at-least-once), but not so much in terms of flaky tests.

I'm looking into this hoping to fix this ASAP.