libnetwork/drivers/ipvlan: fix missing IpvlanFlag field in config JSON
libnetwork/drivers/ipvlan: fix missing IpvlanFlag field in config JSON

Fixes #42542

Signed-off-by: Youfu Zhang <6556e91b726a17e27651c426210a1d126b33b8d2@gmail.com>

thaJeztah/docker,Mokolea/docker,moby/moby,moul/docker,thaJeztah/docker,moul/docker,Ramzec/docker,cpuguy83/docker,thaJeztah/docker,konstruktoid/docker-upstream,trebonian/docker,konstruktoid/docker-upstream,moul/docker,Mokolea/docker,jimjag/docker,moby/moby,konstruktoid/docker-upstream,Ramzec/docker,mahak/docker,konstruktoid/docker-upstream,mahak/docker,trebonian/docker,moby/moby,cpuguy83/docker,cpuguy83/docker,Mokolea/docker,jimjag/docker,thaJeztah/docker,jimjag/docker,Ramzec/docker,jimjag/docker,trebonian/docker,mahak/docker,moul/docker,trebonian/docker,cpuguy83/docker,Mokolea/docker,mahak/docker,moby/moby,Ramzec/docker