Support for both List-Mode and Page-Mode osd attributes. One of
these operations may be added to most other operations.

Define the OSD standard's attribute pages constants and structures
(osd_attributes.h)
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>
Reviewed-by: NBenny Halevy <bhalevy@panasas.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>