Pull up following revision(s) (requested by knahakara in ticket #340):
sys/net/if_vlan.c: revision 1.104
fix vlan panic when vlan is re-configured without destroy.
E.g. the following operation causes this panic.
    ====================
    # ifconfig vlan0 create
    # ifconfig vlan0 vlan 1 vlanif ixg3
    # ifconfig vlan1 create
    # ifconfig vlan1 vlan 1 vlanif ixg2
    # ifconfig vlan1 -vlanif
    # ifconfig vlan1 vlan 1 vlanif ixg2
    panic: kernel diagnostic assertion "new->ple_next == NULL" failed: file "/git/netbsd-src/sys/sys/pslist.h", line 118
    ====================
Pointed out and tested by msaitoh@n.o, fixed by s-yamaguchi@IIJ, thanks.

(snj)