If dummynet_task() is run on a vnet where dummynet is still initialising
(i.e. still running ip_dn_vnet_init()) we can attempt to use an
We can use the existing init_done field to check if the per-vnet
V_dn_cfg is fully set up, if we ensure that it's only set to 1 when
we've done all of the init work.
Reported by: Alfredo Dal'Ava Júnior <email@example.com>
Sponsored by: Rubicon Communications, LLC ("Netgate")