9035 zfs: this statement may fall through

illumos/illumos-gate@46ac8fdfc5a1f9d8240c79a6ae5b2889cbe83553

Reviewed by: Yuri Pankov <yuripv@yuripv.net>
Reviewed by: Andy Fiddaman <omnios@citrus-it.co.uk>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Toomas Soome <tsoome@me.com>