i386 hangs during halt "vnodes remaining... 0 time out"

[Rick Macklem]

With a recent head/current kernel (doesn't happen when running a Dec. 2017 one),
when I do a halt, it gets as far as:

vnodes remaining... 0 time out

and that's it (the time out appears several seconds after the first "0").
With a Dec. 2017 kernel there would be several "0"s printed.
It appears that it is stuck in the first iteration of the sched_sync() loop after
it is no longer in SYNCER_RUNNING state.

Any ideas? rick