RFR: 2363: When jcheck result is too big, it can't be published to Github

[Zhao Song]

Sometimes, a pull request contains too many whitespace errors and it will generate a large jcheck result. Therefore, when the bot is trying  to post it to GitHub, it will fail and keep retrying.

This patch is trying to limit the size of jcheck error message.

-------------

Commit messages:
 - SKARA-2363

Changes: https://git.openjdk.org/skara/pull/1688/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1688&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2363
  Stats: 7 lines in 1 file changed: 3 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/skara/pull/1688.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1688/head:pull/1688

PR: https://git.openjdk.org/skara/pull/1688