MFV 286588: 5820 verify failed in zio_done(): BP_EQUAL(bp, io_bp_orig)

Reviewed by: Alex Reece <alex@delphix.com>
Reviewed by: George Wilson <george@delphix.com>
Reviewed by: Steven Hartland <killing@multiplay.co.uk>
Approved by: Garrett D'Amore <garrett@damore.org>
Author: Matthew Ahrens <mahrens@delphix.com>

illumod/illumos-gate@34e8acef009195effafdcf6417aec385e241796e