Illumos 5820 - verify failed in zio_done(): BP_EQUAL(bp, io_bp_orig)

Illumos 5820 - verify failed in zio_done(): BP_EQUAL(bp, io_bp_orig)

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>

References:
  https://www.illumos.org/issues/5820
  https://github.com/illumos/illumos-gate/commit/34e8acef00

Ported-by: DHE <git@dehacked.net>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3364