RFR: 2387: Revert SKARA-2386 and cache issueProject in JiraHost

[Zhao Song]

In [SKARA-2386](https://bugs.openjdk.org/browse/SKARA-2386), we are using the issueProject name as the key of different maps in PullRequestBotFactory. But they are not unified.

For issueProjectMap, the key is the full name of the issue project like "bugs/JDK". For other maps, the key is only the project name like "JDK".

This will make the factory not be able to generate IssueBot correctly.

Currently, I think maybe it's better to revert [SKARA-2386](https://bugs.openjdk.org/browse/SKARA-2386) and cache the issueProject in JiraHost to fix the problem.

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Commit messages:
 - update
 - add comment
 - Revert "2386: PullRequestBotFactory creates too many IssueBots"
 - Merge branch 'master' into test2387
 - 2387

Changes: https://git.openjdk.org/skara/pull/1690/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1690&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2387
  Stats: 28 lines in 3 files changed: 5 ins; 6 del; 17 mod
  Patch: https://git.openjdk.org/skara/pull/1690.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1690/head:pull/1690

PR: https://git.openjdk.org/skara/pull/1690