vmm, vm-virtio: Restore DeviceManager's devices in a paused state

The same way the VM and the vCPUs are restored in a paused state, all
devices associated with the device manager must be restored in the same
paused state.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/device_manager.rs

@@ -3477,6 +3477,7 @@ impl Snapshottable for DeviceManager {
             if let Some(migratable) = &node.migratable {
                 debug!("Restoring {} from DeviceManager", node.id);
                 if let Some(snapshot) = snapshot.snapshots.get(&node.id) {
+                    migratable.lock().unwrap().pause()?;
                     migratable.lock().unwrap().restore(*snapshot.clone())?;
                 } else {
                     return Err(MigratableError::Restore(anyhow!(