The redirect handling for http2 was a little simple. E.g. not handling
relative URLs.
Fix this using the redirect response parsing function which the http1
protocol handler already uses.
Fixes: QTBUG-100651
Pick-to: 6.3 6.2 5.15
Change-Id: Ic0cec4cacc92707e7a7fde1f4665f80995a6057e
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>