Make ZFS filesystem id persistent across different machines
Use ZFS dataset fsid guid as a unique file system id, similar to what is
done on Illumos/OpenSolaris.
Signed-off-by: Cyril Plisko <cyril.plisko@mountall.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #888