9434 Speculative prefetch is blocked by device removal code
illumos/illumos-gate@47b8d4b884f2dab4e4c6952b40fd740a8fc4ab32
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Approved by: Matt Ahrens <mahrens@delphix.com>
Author: Alexander Motin <mav@FreeBSD.org>