RFR: 1886: Only configure CSRIssueBot for issuetrackers where we have CSR configured

[Zhao Song]

As Erik said in the issue, now the PullRequestBotFactory creates a CSRIssueBot for every IssueTracker configured. It is unnecessary and would trigger some errors.

In this patch, PullRequestBotFactory only creates a CSRIssueBot for the IssueTracker which is associated with any CSR enabled repository.

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Commit messages:
 - SKARA-1886

Changes: https://git.openjdk.org/skara/pull/1506/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1506&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1886
  Stats: 74 lines in 2 files changed: 37 ins; 10 del; 27 mod
  Patch: https://git.openjdk.org/skara/pull/1506.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1506/head:pull/1506

PR: https://git.openjdk.org/skara/pull/1506