Remove permission checks on local files and remove `safcm fixperms`

Remove permission checks on local files and remove `safcm fixperms`

The intended use case was to "protect" users against unexpected behavior
when migrating from a legacy system configuration management. This no
longer applies.

In addition, needing to run fixperms is generally annoying and makes the
tests more complex and fragile.

`safcm fixperms` is kept as command not to break existing workflows. It
has no effect now.