RFR: 1885: Add method deleteDeployKeys to HostedRepository

[Zhao Song]

The method deleteDeployKeys is designed to delete deploy keys from this repository.

-------------

Commit messages:
 - fix import
 - SKARA-1885

Changes: https://git.openjdk.org/skara/pull/1505/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1505&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1885
  Stats: 85 lines in 7 files changed: 80 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/skara/pull/1505.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1505/head:pull/1505

PR: https://git.openjdk.org/skara/pull/1505