RFR: Avoid posting integrated notices for old RFR threads

[Robin Westberg]

Hi all,

Please review this change that checks for a "legacy" integration notice before posting an integration notice again, to
improve the transition from the old notifier to the new one.

Best regards,
Robin

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Commit messages:
 - Avoid posting integrated notices for old RFR threads

Changes: https://git.openjdk.java.net/skara/pull/607/files
 Webrev: https://webrevs.openjdk.java.net/skara/607/webrev.00
  Stats: 88 lines in 2 files changed: 85 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/skara/pull/607.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/607/head:pull/607

PR: https://git.openjdk.java.net/skara/pull/607