Integrated: Avoid checking closed PRs, handle the "skipped" state of a GitHub check

[Robin Westberg]

This small fix avoids a few problems with the latest check updates.

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Commit messages:
 - Merge remote-tracking branch 'upstream/master' into check_states
 - Avoid checking closed PRs, handle the "skipped" state of a GitHub check

Changes: https://git.openjdk.java.net/skara/pull/865/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=865&range=00
  Stats: 5 lines in 2 files changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/865.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/865/head:pull/865

PR: https://git.openjdk.java.net/skara/pull/865