app-emulation/libvirt: Check for more kernel configs for virtual net

app-emulation/libvirt: Check for more kernel configs for virtual net

After 7431b3eb9a05068e4b Libvirt starts to create chains to
insert rules into instead of placing them right at the top level
chains. These private chains are created on daemon startup and
the referenced commit made all 6 tables required (combination of
default 3 tables: nat, filter and mangle for both IPv4 and IPv6).
This was later refined in 686803a1a2e1e06, but it still makes
sense for ebuild to check for all tables being enabled in the
kernel because both IPv4 and IPv6 are used widely.

Package-Manager: Portage-2.3.62, Repoman-2.3.12
Closes: https://bugs.gentoo.org/681010
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Matthias Maier <tamiko@gentoo.org>