RFR: 2039: Only post ApprovalNeededComment when the user hasn't applied for maintainer approval for all the issues

[Zhao Song]

In [SKARA-1949](https://bugs.openjdk.org/browse/SKARA-1949), we introduced /approval command and at the same time, we let the bot post ApprovalNeededComment when the pull request is reviewed.

As Kevin Rushforth suggested, the bot shouldn't post ApprovalNeededComment if the user already applied for at least one of the issues.

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Commit messages:
 - update
 - SKARA-2039

Changes: https://git.openjdk.org/skara/pull/1606/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1606&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2039
  Stats: 28 lines in 3 files changed: 13 ins; 13 del; 2 mod
  Patch: https://git.openjdk.org/skara/pull/1606.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1606/head:pull/1606

PR: https://git.openjdk.org/skara/pull/1606