RFR: Improve PR bot startup performance

Tue Oct 6 07:51:00 UTC 2020

The PR bot can start with only looking at recently updated PRs while caches are being populated due to a restart. This
will improve response times after new code is deployed.

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Commit messages:
 - Improve PR bot startup performance

Changes: https://git.openjdk.java.net/skara/pull/860/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=860&range=00
  Stats: 34 lines in 2 files changed: 29 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/skara/pull/860.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/860/head:pull/860

PR: https://git.openjdk.java.net/skara/pull/860