compilation fixes

Author: dobrac

src/vmm/src/device_manager/pci_mngr.rs

@@ -311,7 +311,9 @@ impl<'a> Persist<'a> for PciDevices {
                              snapshotting yet"
                         );
                     } else {
-                        block_dev.prepare_save()?;
+                        if let Err(err) = block_dev.prepare_save() {
+                            warn!("Failed to prepare block device for save: {:?}", err);
+                        }
                         let device_state = block_dev.save();
                         state.block_devices.push(VirtioDeviceState {
                             device_id: block_dev.id().to_string(),

src/vmm/src/device_manager/persist.rs

@@ -265,7 +265,9 @@ impl<'a> Persist<'a> for MMIODeviceManager {
                              snapshotting yet"
                         );
                     } else {
-                        block.prepare_save()?;
+                        if let Err(err) = block.prepare_save() {
+                            warn!("Failed to prepare block device for save: {:?}", err);
+                        }
                         let device_state = block.save();
                         states.block_devices.push(VirtioDeviceState {
                             device_id,