prior to zvol and mountcritlocal resulting in ZVOLs (swap and
virtual machine UFS filesystems) being unavailable, leading to
boot failures.
We move the zpool import from zfs to a new zpool script, with the
-N option to avoid mounting datasets while making the ZPOOL's
datasets available for "legacy" mount (mountpoint=legacy) and ZVOLs
available for subsequent use for swap (in the zvol rc sript) or
for UFS or other filesystems in fstab(5), mounted by mountcritlocal.
Reviewed by: freqlabs (previous version)
Differential Revision: https://reviews.freebsd.org/D26185
74e2b24f2c