ifconfig: add static bridge addresses for vlan 0, not 1

Since fd7edfcdc3 ("bridge: fix lookup for untagged packets in
bridge_transmit()") and b0e38a1373 ("bridge: distinguish no vlan and
vlan 1") we do a better job of distinguishing between untagged and VLAN
1 traffic.

However, ifconfig still defaulted to adding addresses for VLAN 1, rather
than for untagged traffic. Change this to be the most common (i.e.
untagged) option.

Reviewed by: zlei, philip
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D42188

(cherry picked from commit 6ace92326f3cc4bbee9b74f6b656cb13699a78a2)