add Shadow root olderShadowRoot Attributes test
Merge branch 'submissions/kyohei8-ShadowRoot-olderShadowRoot' of https://github.com/kyohei8/web-platform-tests into kyohei8-submissions/kyohei8-ShadowRoot-olderShadowRoot

Conflicts:
	shadow-dom/elements-and-dom-objects/shadowroot-object/shadowroot-attributes/test-014.html
Merge branch 'kyohei8-submissions/kyohei8-ShadowRoot-olderShadowRoot'

Manually merge pull request #882 from kyohei8:submissions/kyohei8-ShadowRoot-olderShadowRoot

Comments from @hayatoito is also applied (better variable name, not
reusing the same variable for different purpose).