RFR: 1129: [REDO] The mlbridge bot occasionally posts the same comments twice on Github

[Erik Joelsson]

Redo of SKARA-1058. The patch is exactly the same as I don't think it was the cause for SKARA-1128.

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Commit messages:
 - SKARA-1129

Changes: https://git.openjdk.java.net/skara/pull/1213/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1213&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1129
  Stats: 38 lines in 10 files changed: 9 ins; 18 del; 11 mod
  Patch: https://git.openjdk.java.net/skara/pull/1213.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1213/head:pull/1213

PR: https://git.openjdk.java.net/skara/pull/1213