vfio: Add a public function to retrive VFIO container

The VFIO container is the object needed to update the VFIO mapping
associated with a VFIO device. This patch allows the device manager
to have access to the VFIO container.

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

vmm/src/device_manager.rs

@@ -1006,6 +1006,8 @@ impl DeviceManager {
                     VfioDevice::new(&device_cfg.path, device_fd.clone(), vm_info.memory.clone())
                         .map_err(DeviceManagerError::VfioCreate)?;
 
+                let _vfio_container = vfio_device.get_container();
+
                 let mut vfio_pci_device = VfioPciDevice::new(vm_info.vm_fd, allocator, vfio_device)
                     .map_err(DeviceManagerError::VfioPciCreate)?;