5393 spurious failures from dsl_dataset_hold_obj()

Author: Justin T. Gibbs <justing@spectralogic.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Will Andrews <willa@spectralogic.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Steven Hartland <killing@multiplay.co.uk>
Approved by: Dan McDonald <danmcd@omniti.com>

illumos/illumos-gate@e1f3c208abda53769a6531bb1141618555273460