restore the previous semantics wrt if up, tunnel, and address config.

restore the previous semantics wrt if up, tunnel, and address config.

this is a port of the change made to if_etherip.c r1.35 to allow
addresses to be configured before the tunnel is configured.

this rollback is particularly annoying on gre with keepalives.
keepalives rely on the interface rdomain and tunnel rdomain to be
the same, which the rolled back semantics checked. now it is possible
to create an invalid configuration and not get any feedback about
it.