CP-5831: Productise removal of lvm2-lvchange-idempotent.patch

Part of changes required to remove lvm2-lvchange-idempotent.patch.
LVM throws an error if an LV that is already RO is set to RO again
or an RW lv is set to RW. Added additional check on XS side to check
LV status before changing access permissions.

Signed-off-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>

GitHub: closes #26 on xapi-project/sm