CA-163782: Add a reason for o_direct on VDI.attach
CA-163782: Add a reason for o_direct on VDI.attach

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>

Conflicts:
	ocaml/xapi/sm.ml
	ocaml/xapi/sm_exec.ml
	ocaml/xapi/smint.ml
	ocaml/xapi/storage_access.ml
	ocaml/xapi/storage_impl_test.ml
	ocaml/xenops/xenops_server_xen.ml

johnelse/xcp-idl,xapi-project/message-switch,djs55/xcp-idl,euanh/xcp-idl,xapi-project/message-switch,xapi-project/message-switch,Chunjie/xcp-idl