Measure `git clone` speeds on current NFS drives

In gitlab-com/infrastructure#2261, we have some excellent data on raw disk speeds.

For the sake of completeness, we still need to see how fast/slow this would be if we were to use a git clone approach with Geo.

Can we:

1. Sample a number (e.g. 1000) of repositories on a local NFS server
2. Test how fast/slow this would be if we were to issue a large number of git clone in parallel

/cc: @ernstvn, @sitschner, @pcarranza, @ilyaf