MFV r302661: 7082 bptree_iterate() passes wrong args to zfs_dbgmsg()

illumos/illumos-gate@10e67aa0db0823d5464aafdd681f3c966155c68e
https://github.com/illumos/illumos-gate/commit/10e67aa0db0823d5464aafdd681f3c966
155c68e

https://www.illumos.org/issues/7082

upstream
DLPX-40542 bptree_iterate() passes wrong args to zfs_dbgmsg()

Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Matthew Ahrens <mahrens@delphix.com>