selinux: also try the netlink-based fallback and continue on permission error

selinux: also try the netlink-based fallback and continue on permission error

Fedora Rawhide still has the old policy, so selinux prevents our selinux code
from checking if selinux is enabled. But it seems smart to fall back to the old
API anyway.

Follow-up for fd5e402fa9377f2860e02bdb5b84d5f5942e73f4.

Both the reference policy [1] and Fedora selinux policy [2] needed to be
updated, so it's likely that this will impact other distros too.

[1] https://github.com/SELinuxProject/refpolicy/pull/308
[2] https://github.com/fedora-selinux/selinux-policy/pull/464