RFR: Improve logging in PR bot

[Erik Joelsson]

This very minor patch adds the repo names to log messages in `getPeriodicItems()`. I'm going to look into performance issues with the bots, and just seeing a bunch of


Fetching all open pull requests
Fetching all open pull requests


in the log without any further context isn't helping.

I also stumbled over an unused import as well as a bad use of LinkedList while in the area.

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Commit messages:
 - Improve logging

Changes: https://git.openjdk.org/skara/pull/1347/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1347&range=00
  Stats: 4 lines in 1 file changed: 0 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/skara/pull/1347.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1347/head:pull/1347

PR: https://git.openjdk.org/skara/pull/1347