[SCSI] attribute_container: update to use the group interface

This patch is the beginning of moving the attribute_containers to use
attribute groups exclusively.  The attr element is now deprecated and
will eventually be removed (along with all the hand rolled code for
doing exactly what attribute groups do) when all the consumers are
converted to attribute groups.

Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>