The node (and child nodes) is initialized in sysctl_net_pktq_setup, but the call
of sysctl_net_pktq_setup is skipped unexpectedly.
sysctl_net_pktq_setup is skipped if in6_present is false that indicates the
netinet6 component isn't loaded on rump kernels. However the flag is
accidentally always false because the flag is turned on in in6_dom_init that is
called after if_sysctl_setup on both normal and rump kernels.
Fix the issue by moving if_sysctl_setup after in6_dom_init (domaininit on normal
kernels). This fix is ad-hoc but good enough for netbsd-8. We should refine
the initialization order of network components in the future.
Pointed out by hikaru@
1350b04367