CP-8378: Make use of suspend-image format flag

Start Xcp_service with upgrade logic to handle calls to the server from clients
using an older interface.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
CP-8378: Infer image format from disk layout for VM.resume

The resume interface can remain unaltered since the format of the suspend image
can be infered as legacy if it contains a filesystem. Otherwise it is deemed to
be the current format.

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