4689 IDMAP: idmap_getwinnamebyuid() and idmap_getwinnamebygid() fails for empty domains
Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>
Reviewed by: Gordon Ross <gordon.ross@nexenta.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Garrett D'Amore <garrett@damore.org>
	[illumos-gate merge]

commit 8ce3a03883b8748c139aa8c412b64dcc7aaee1a1
    4689 IDMAP: idmap_getwinnamebyuid() and idmap_getwinnamebygid() fails for empty domains