merge branch 'pr-2317'

Ted Yu (1):
  Defer netns.Close() after error check

LGTMs: @AkihiroSuda @cyphar
Closes #2317

libcontainer/container_linux.go

@@ -1335,11 +1335,11 @@ func (c *linuxContainer) Restore(process *Process, criuOpts *CriuOpts) error {
 			// The <key> needs to be the same as during checkpointing.
 			// We are always using 'extRootNetNS' as the key in this.
 			netns, err := os.Open(nsPath)
-			defer netns.Close()
 			if err != nil {
 				logrus.Errorf("If a specific network namespace is defined it must exist: %s", err)
 				return fmt.Errorf("Requested network namespace %v does not exist", nsPath)
 			}
+			defer netns.Close()
 			inheritFd := new(criurpc.InheritFd)
 			inheritFd.Key = proto.String("extRootNetNS")
 			// The offset of four is necessary because 0, 1, 2 and 3 is already