RFR: Backport issues can be open, use proper link relationship

[Robin Westberg]

When looking for eligible backport issues, consider open ones as well.

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Commit messages:
 - Backport issues can be open, use proper link relationship

Changes: https://git.openjdk.java.net/skara/pull/966/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=966&range=00
  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/966.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/966/head:pull/966

PR: https://git.openjdk.java.net/skara/pull/966