If we're not running on xen, don't ask xenopsd-xc about memory

Signed-off-by: David Scott <dave.scott@citrix.com>
Query domain zero memory policy from squeezed

The domain zero memory policy is owned by squeezed, not xapi,
and therefore we should query it and reflect it in the datamodel.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
If we aren't running xen, then we don't have I/O virtualisation

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #1740 from djs55/more-fixes

xenserver-core: allow startup without xen