With the recent change, 'system' headers gone: not in the test code anymore,
so, for example OPENSSL_VERSION_NUMBER is undefined, making the test
to select a wrong code-path - 'h2c', instead of encrypted h2.
Pick-to: 6.2
Pick-to: 6.1
Change-Id: I3b201e21fac56875c9045c7463e2ae69af4c6470
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>