recent VFS_MOUNT changes and system hangs

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

Hi!

When I boot multiuser with root on nfs, I figured out
the umount -a in /etc/rc.d/root causes a system hang.
Further, the system hangs on shutdown/reboot after
syslogd got signal 15.

Tonnerre boots netbsd 4 with root on nfs successfully.
/etc/rc.d/root hasn't been changed since then.

Luke Mewburn pointed to recent VFS_MOUNT changes,
that may broke boot with root on nfs.

Christoph