Merge pull request #979 from hmeng-19/fix_chdir_err

Fix the err info of chdir(cwd) failure

libcontainer/init_linux.go

@@ -144,7 +144,7 @@ func finalizeNamespace(config *initConfig) error {
 	}
 	if config.Cwd != "" {
 		if err := syscall.Chdir(config.Cwd); err != nil {
-			return err
+			return fmt.Errorf("chdir to cwd (%q) set in config.json failed: %v", config.Cwd, err)
 		}
 	}
 	return nil