Each pullmirror job runs two FindAllTags Gitaly GRPC calls

Pullmirrors are the most expensive Sidekiq fleet in terms of Gitaly resource used, by some margin.

Of the pull mirror jobs, the most expensive single call is the FindAllTags call. I am still investigating why this is, but this is fairly inconsequential to this issue.

Most surprisingly, each pullmirror job makes two FindAllTags calls for each pullmirror job.

Reducing this from twice to once in each job should be fairly easy. We should do it as pullmirrors are the most likely cause of latency problems on GitLab.com right now.

https://log.gitlab.net/goto/62fa49725ebb73f6e8b5391cc4a686dd