[XHR] Move the Cache-Control test from /inspector to /xmlhttprequest.

Move a test that tests that XHR respects Cache-Control request header
from LayoutTests/http/tests/inspector to LayoutTests/http/tests/xmlhttprequest.

BUG=333804
R=tyoshino

Review URL: https://codereview.chromium.org/149873004

git-svn-id: svn://svn.chromium.org/blink/trunk@166099 bbb929c8-8fbe-4397-9dbb-9b2b20218538