RFR: 1890: Add method getExpiredDeployKeys

[Zhao Song]

Add a new method called getExpiredDeployKeys in HostedRepository

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Commit messages:
 - SKARA-1890

Changes: https://git.openjdk.org/skara/pull/1508/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1508&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1890
  Stats: 93 lines in 7 files changed: 89 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/skara/pull/1508.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1508/head:pull/1508

PR: https://git.openjdk.org/skara/pull/1508