Repo plugin shall not use by default flag "-no-repo-verify" when using custom repo mirror "-repo-url", but an option should be added to control whether to perform this check or not.

Use case: using internal mirror of upstream "gerrit repo" repository, so I can perform a build without accessing Internet

For the moment the option "--no-repo-verify"  is not working, but I don't need it since I'm just using a mirror of official repositories, so all the tags are signed with GPG.