The socket is typically owned by the priv-user, and inaccessible by the target user, so just allowing access to the directory is not enough. This change fixes this oversight and add checks that will also be useful for merging #1.
Signed-off-by: Ophestra <cat@gensokyo.uk>
# Conflicts:
# test/sandbox/case/device.nix
# test/sandbox/case/tty.nix