4756 metaslab_group_preload() could deadlock
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com>
Approved by: Garrett D'Amore <garrett@damore.org>
	[illumos-gate merge]

commit 30beaff42d8240ebf5386e8b7a14e3d137a1631f
    4756 metaslab_group_preload() could deadlock