RFR: Use a different (empty) thread prefix for failed automerge PRs

[Robin Westberg]

Hi all,

Please review this change that skips the "RFR: " prefix on mailing list threads initiated by a failed automerge PR.

Best regards,
Robin

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Commit messages:
 - Use a different (empty) thread prefix for failed automerge PRs

Changes: https://git.openjdk.java.net/skara/pull/542/files
 Webrev: https://webrevs.openjdk.java.net/skara/542/webrev.00
  Stats: 67 lines in 5 files changed: 60 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/skara/pull/542.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/542/head:pull/542

PR: https://git.openjdk.java.net/skara/pull/542