Investigate auto-test failures

Since we moved tls-backends into qtbase/plugins we noticed a strange behaviour. We now can build more than one TLS plugin for a single platform. For example: "openssl-runtime" and "securetransport". Then, if, say, 'openssl' backend is not-available suddenly (e.g. I forgot to set paths properly and OpenSSL symbols were not resolved) - some auto-tests are failing, even though SecureTransport backend was selected by QSslSocket (and it does not fail if only SecureTransport plugin was built, only when two backends/plugins were build simultaneously). Probably, a matter of both 'features' defined and not properly fixed test in some places yet.