RFR: 1899: Stop notifiers when the PR bot fails to retrieve issue temporarily

[Zhao Song]

A user reported that skara bot was editing the links in [JDK-8306027](https://bugs.openjdk.org/browse/JDK-8306027) and generated many mail spam.

As Erik said, [JDK-8306781](https://bugs.openjdk.org/browse/JDK-8306781) is the CSR of JDK-8306027. JDK-8306781 was updated few hours ago and it triggered CSRIssueWorkItem to update the pull request(https://github.com/openjdk/jdk/pull/13661). However, when updating the pr, the bot failed to retrieve JDK-8306027 and printed "⚠️ Temporary failure when trying to retrieve information on issue 8306027" in the pr body. This update of PR body triggered PullRequestWorkItem in NotifyBot and make issueNotifier to update links to PR issues.

To resolve this issue, I think we could stop the notifiers when the bot finds temporary issue failure.

Once the temporary issue failure has been resolved, the pr body will be updated again and it will trigger the notifiers to work.

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Commit messages:
 - SKARA-1899

Changes: https://git.openjdk.org/skara/pull/1512/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1512&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1899
  Stats: 91 lines in 6 files changed: 87 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/skara/pull/1512.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1512/head:pull/1512

PR: https://git.openjdk.org/skara/pull/1512