Previously --nofilesystem=host only removed specifically access to the
`host` permissions, and not necessarily other filesystems (like `home`
or `/some/path`). This isn't very useful to limit access because you
don't know what other filesystems the app may have access too.
We change this to mean that `--nofilesystem=host` removes *all* filesystem
access from the parent layer, and `--nofilesystem=home` removes all
file access to the homedir and paths inside it.
The available layers are, in order:
* app permissions
* overrides
* commandline args
This allows you to start from scratch with the filesystem permissions
in the overrides or the commandline. This is a small change in
behaviour, but not a lot of things use --nofilesystem, and the ones
that do probably expects this behaviour.
(cherry picked from commit e2c8863fb62301cb05c64bbb32b04446e88ce11a)
d36382dd4d