RFR: 1316: Review comment on a commit triggers error in CommitCommentsWorkItem

[Erik Joelsson]

Add additional filtering of notes when looking for comments on commits on Gitlab, to avoid picking up comments on other things, such as MR diffs.

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Commit messages:
 - SKARA-1316

Changes: https://git.openjdk.java.net/skara/pull/1275/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1275&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1316
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/1275.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1275/head:pull/1275

PR: https://git.openjdk.java.net/skara/pull/1275