5164 space_map_max_blksz causes panic, does not work
5165 zdb fails assertion when run on pool with recently-enabled spacemap_histogram feature
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com>
Approved by: Dan McDonald <danmcd@omniti.com>