Fix LFS timeouts when trying to save large files

The following was happening:

1. Workhorse stores an LFS file in /var/opt/gitlab/gitlab-rails/shared/lfs-objects/tmp/uploads
2. CarrierWave then renames the file to a temporary directory (e.g. /opt/gitlab/embedded/service/gitlab-rails/tmp)
3. CarrierWave then renames the file to its final location (e.g. /var/opt/gitlab/gitlab-rails/shared/lfs-objects)

When the LFS upload path was on a different filesystem than the Rails installation, step 2 could take a longer than 10 seconds, at which point Workhorse would time out with "badgateway: failed after 10s: context canceled".

This change makes the work path the same root as the LFS storage path, preventing moves across filesystems.

Closes #33218 (closed)