3771 kmdb hangs when reading an invalid address
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Jeff Biseda <jbiseda@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Albert Lee <trisk@nexenta.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>
	[illumos-gate merge]

commit 982e63f0dc541ca7cc5d69cf6504d5218a48434d
    3771 kmdb hangs when reading an invalid address