HTTP: Secure Cookies Should only be sent on secure connections

Secure Cookies should only be sent over secure connections.

QtWebKit currently fails the following test:

LayoutTests/http/tests/xmlhttprequest/cookies.html

This is because QNetworkCookieJar::cookiesForUrl returns secure
cookies even when the connection is not secure.

A 'secure' cookie is set by response headers from a http server as follows:

'Set-Cookie: cookie-name=value; secure'

Correct QNetworkCookieJar::cookiesForUrl to ignore secure cookies when the
url in the request is not 'https://'.