MFV r303077:
7072 zfs fails to expand if lun added when os is in shutdown state

illumos/illumos-gate@c39a2aae1e2c439d156021edfc20910dad7f9891
https://github.com/illumos/illumos-gate/commit/c39a2aae1e2c439d156021edfc20910dad7f9891

https://www.illumos.org/issues/7072

upstream:
38733 zfs fails to expand if lun added when os is in shutdown state
DLPX-36910 spares and caches should not display expandable space
DLPX-39262 vdev_disk_open spam zfs_dbgmsg buffer

Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Alex Reece <alex@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: George Wilson <george.wilson@delphix.com>