5809 Blowaway full receive in v1 pool causes kernel panic

Author: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Alex Reece <alex@delphix.com>
Reviewed by: Will Andrews <will@freebsd.org>
Approved by: Gordon Ross <gwr@nexenta.com>

illumos/illumos-gate@f40b29ce2a815bcc0787acf6f520a2b74258b785