Add ipadm and nwam options to allow designating a DHCP address as the primary interface
ifconfig has the following option:
Defines the interface as the primary. The interface is defined
as the preferred one for the delivery of client-wide
configuration data. Only one interface can be the primary at
any given time. If another interface is subsequently selected
as the primary, it replaces the previous one. Nominating an
interface as the primary one will not have much significance
once the client work station has booted, as many applications
will already have started and been configured with data read
from the previous primary interface.
Neither ipadm nor nwamd has an optional to allow designating an interface as such, but it would be convenient to have this.