4036 fix blkdev uninitialized return values
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Hans Rosenfeld <hans.rosenfeld@nexenta.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
	[illumos-gate merge]

commit a0cb694bef8ce5b375d89d042945f0e24bbd4026
    4036 fix blkdev uninitialized return values