MFC r297507: MFV r297504:
6681 zfs list burning lots of time in dodefault() via dsl_prop_*

Reviewed by: Patrick Mooney <patrick.mooney@joyent.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Matthew Ahrens <mahrens@delphix.com>
Author: Alex Wilson <alex.wilson@joyent.com>

illumos/illumos-gate@d09e4475f635b6f66ee68d8c17a32bba7be17c96