Project dashboard appears to be loading tags on every request

When requesting a project dashboard (https://gitlab.com/gitlab-org/gitlab-ce in particular) between 3 and 6 seconds is spent in Rugged::TagCollection#each. Most likely this is used for the button that displays the number of tags. Whatever it is that uses this method should cache the output whenever possible so we don't hit Git on every request.

The following screenshot shows the timings spent in this method during a time window where I ran siege -i -c 4 -t 30m 'https://gitlab.com/gitlab-org/gitlab-ce' to hammer the gitlab-org/gitlab-ce dashboard: