MFC r294811: MFV r294810: 6414 vdev_config_sync could be simpler
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Will Andrews <will@firepipe.net>
illumos/illumos-gate@eb5bb58421f46cee79155a55688e6c675e7dd361