importer: tweak previous, first pass
importer: tweak previous, first pass

/dev/zfs/pool does not exist so we can do a "zfs/pool" input
in alignment with gmirror and graid inputs.  Move the probing
after zfs load to be able to unload again also.

opnsense/core,opnsense/core,opnsense/core,opnsense/core,opnsense/core,opnsense/core