repo: Do not even try to set up GPG with opt.no_repo_verify

In order to be able to use "--no-repo-verify" to work around an issue with
gpg-agent and long socket paths (see e.g. [1]), this change avoids GPG
being set up at all if that option is passed.

[1] https://github.com/elastic/elasticsearch/issues/17053

Change-Id: I1e5cbd8be2dc0084f12afe0ca33c789fdbc6fef9
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/251108


Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Mike Frysinger <vapier@google.com>