Geo: Don't attempt to expire the cache after a failed clone

In https://sentry.gitlap.com/gitlab/gitlabcom/issues/142045/events/oldest/, I saw that one of the repos was > 1 GB, and it failed to clone for some reason. I suspect it doesn't clone with git 2.14, but will work for 2.16.

As a result, the repo is broken/empty. We still attempt to expire the cache, which throws up a Gitaly error.