RFR: 1365: Draft PRs do not get extra time before auto closing

[Magnus Ihse Bursie]

The PullRequestPrunerBot automatically closes PRs that have been inactive for too long. The maxAge is configurable, and we have it set to 28 days for most repos on Github. [SKARA-831](https://bugs.openjdk.java.net/browse/SKARA-831) tried to give draft PRs double the time before being auto closed. Unfortunately, that fix wasn't enough, as it only affects the printed message and not the actual age check.

I tried to add a unit test for this, but in the end I could find no reliable way to do this. I don't want to rely on timings. And the only other thing I could think of checking was the message printed -- but that was already "correct" so it would not verify this bug anyway.

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Commit messages:
 - 1365: Draft PRs do not get extra time before auto closing

Changes: https://git.openjdk.java.net/skara/pull/1293/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1293&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1365
  Stats: 4 lines in 1 file changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/skara/pull/1293.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1293/head:pull/1293

PR: https://git.openjdk.java.net/skara/pull/1293