RFR: 1629: Limit how far back maxUpdatedAt can be set in PullRequestPoller

[Erik Joelsson]

After having observed the PullRequestPoller in action for a bit, I've noticed some weird behavior. Say a very old open PR A exists, and there is a closed PR B that is newer (but older than the 7 day initial query limit). Then on the first round, PR A will be returned and maxUpdatedAt will be set to updatedAt of PR A. On the second round, this will cause PR B to be returned. This is causing some weird behavior, resurrecting very old closed PRs that have problems with them.

This patch fixes this by putting a hard limit on how far back we query for the updatedAt field.

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Commit messages:
 - SKARA-1629

Changes: https://git.openjdk.org/skara/pull/1395/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1395&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1629
  Stats: 36 lines in 2 files changed: 33 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/skara/pull/1395.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1395/head:pull/1395

PR: https://git.openjdk.org/skara/pull/1395