RFR: 1691: Run Jcheck twice in CheckRun if .jcheck/conf has changed

[Zhao Song]

When a pr is created, pr bot will run jcheck to check whether this commit is good. However, currently, we only run jcheck with the configuration from the target branch. Sometimes, user wants to modify jcheck configuration and accidentally messes up the format. In this case, pr bot would not be able to find this problem. After this commit with badly formatted jcheck configuration integrated, all the jcheck will fail and our bot gets stuck into a retry loop.

In this patch, if jcheck configuration file is updated, the bot will run jcheck twice, once with the configuration in the target and once with the new one in the source. So if the new configuration has any problem, it will became an integration blocker.

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Commit messages:
 - SKARA-1691
 - Merge branch 'master' into SKARA-1691
 - continue working after merge master

Changes: https://git.openjdk.org/skara/pull/1439/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1439&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1691
  Stats: 185 lines in 9 files changed: 181 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/skara/pull/1439.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1439/head:pull/1439

PR: https://git.openjdk.org/skara/pull/1439