domain: stash xen_domctl_createdomain flags in struct domain

domain: stash xen_domctl_createdomain flags in struct domain

These are canonical source of data used to set various other flags. If
they are available directly in struct domain then the other flags are no
longer needed.

This patch simply copies the flags into a new 'options' field in
struct domain. Subsequent patches will do the related clean-up work.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>