Geo: Wrong project statistics after clone

From https://gitlab.slack.com/archives/C101F3796/p1536271858000100:

It looks like the project statistics only showed 3.4 GB, but in actuality it was taking 222 GB. The last push was 3 months ago.

This could have happened in multiple ways:

1. Project was synched by Geo, but the size got bigger because we had a lot of loose objects (this repository had lots of these).
2. The statistics were wrong to begin with, and we never refreshed since there were no pushes.

We may want to consider:

1. Periodically refreshing the project statistics, especially for projects that have not received in a push in a while.
2. After a failover/switchover, do a full refresh of project statistics.