(#5496) zpool provider supports new 'zpool status' format

The "Solaris 10 9/10 release (Update 9)" update changed the output from
the "zpool status" command, which breaks the zpool provider. The format
basically changed from "vdev" to "vdev-n" (ex: "mirror" to "mirror-0"),
which the current provider doesn't recognize.

This fix changes the way vdev's are checked by the zpool provider, to
support either format.

Reviewed-By: Nick Lewis