This change makes ipvlan master parameter optional.
Default to default route interface as macvlan does.
Signed-off-by: Tomofumi Hayashi <tohayash@redhat.com>
For IP allocation schemes that cannot be interface agnostic, the
ipvlan plugin can be chained with an earlier plugin that handles this
logic. If "master" is omitted from the ipvlan configuration, then the
previous Result must contain a single interface name for the ipvlan
plugin to enslave. If "ipam" is omitted, then the previous Result is
used to configure the ipvlan interface.
For IP allocation schemes that cannot be interface agnostic, master can be set
to "ipam". In this configuration, the IPAM plugin is required to return a single
interface name for the ipvlan plugin to enslave.
