Only a workaround.  Need to take this to FreeBSD.

The default is to reboot anyway.  For everybody importing a backup
that has interface mismatches this means the backup did not come
from the same system, so it must be adapted on the console instead.

Caused by:	Omitted /var/run boot up purge

Remove the size settings for those mount points as a preparation,
because tmpfs does not need an upper bound.  Hardcode everything
now, replace mfs with tmpfs in an upcoming commit.