MFC r337017: MFV r337014:
9421 zdb should detect and print out the number of "leaked" objects
9422 zfs diff and zdb should explicitly mark objects that are on the deleted queue

illumos/illumos-gate@20b5dafb425396adaebd0267d29e1026fc4dc413

Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Approved by: Matt Ahrens <mahrens@delphix.com>
Author: Paul Dagnelie <pcd@delphix.com>