runc delete: do not ignore error from destroy

If container.Destroy() has failed, runc destroy still return 0, which is
wrong and can result in other issues down the line.

Let's always return error from destroy in runc delete.

For runc checkpoint and runc run, we still treat it as a warning.

Co-authored-by: Zhang Tianyang <burning9699@gmail.com>
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

delete.go

@@ -18,8 +18,7 @@ func killContainer(container *libcontainer.Container) error {
 	for i := 0; i < 100; i++ {
 		time.Sleep(100 * time.Millisecond)
 		if err := container.Signal(unix.Signal(0)); err != nil {
-			destroy(container)
-			return nil
+			return container.Destroy()
 		}
 	}
 	return errors.New("container init still running")
@@ -80,13 +79,11 @@ status of "ubuntu01" as "stopped" the following will delete resources held for
 		}
 		switch s {
 		case libcontainer.Stopped:
-			destroy(container)
+			return container.Destroy()
 		case libcontainer.Created:
 			return killContainer(container)
 		default:
 			return fmt.Errorf("cannot delete container %s that is not stopped: %s", id, s)
 		}
-
-		return nil
 	},
 }