Illumus 5693 - ztest fails in dbuf_verify: buf[i] == 0, due to dedup …

…and bp_override

5693 ztest fails in dbuf_verify: buf[i] == 0, due to dedup and bp_override
Reviewed by: George Wilson <george@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Bayard Bell <buffer.g.overflow@gmail.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/5693
  illumos/illumos-gate@7f7ace3

Ported-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#3231

module/zfs/zio.c

@@ -1043,8 +1043,6 @@ zio_write_bp_init(zio_t *zio)
 			zio->io_pipeline |= ZIO_STAGE_DDT_WRITE;
 			return (ZIO_PIPELINE_CONTINUE);
 		}
-		zio->io_bp_override = NULL;
-		BP_ZERO(bp);
 	}
 
 	if (!BP_IS_HOLE(bp) && bp->blk_birth == zio->io_txg) {