lfs: avoid a potential variable reference before assignment error in cmdserver A coworker hit this once yesterday when pulling in thg (a retry worked), and then I hit it with strip after a pull. I had a difficult time recreating a test for this (at least one of the tricks was to not use '-R', which seems to cause reposetup() to be called for each command), so I'm not sure how large of a window there actually is for this. Calling reposetup() *after* the requirement is added will skip the hook entirely. The other issue I had was adding a couple `ui.status()` lines around the check that installs the hook. On Windows, the cmdserver process ballooned to 1.6GB and hung. Changing that to `ui.warn()` avoided the hang. It also hung on macOS, but without the large memory usage.