Static files are not updated when using `galaxy_manage_subdomain_static`

[mira-miracoli]

After we upgraded EU to 24.0, we noticed, that some subdomains were having old CSS files. see (not public):

• https://github.com/usegalaxy-eu/issues/issues/537

This comes potentially from the ignore_existing flag I set to rsync the files from Galaxy's default static directory to the subdomain's static directory. The reason was, that ansible would touch files that are different for the subdomain on every plabook run. It would first overwrite them with the rsync command and than overwrite them again when it copies over subdomain's custom file. My idea to solve this would be using this: {{ __galaxy_client_build_version }} != {{ __galaxy_current_commit_id }} as indicator that Galaxy has been updated and in that case omit the ignore_existing flag. Does that sound sensible to you @hexylena @natefoo or do you think there is a better approach?