Not entirely clear why, but when building the certificate chain for a
peer the system certificate store is searched for root certificates.
General expectation is that after calling
`sslConfiguration.setCaCertificates()` the system certificates will
not be taken into consideration.
To work around this behavior, we do a manual check that the root of the
chain is part of the configured CA certificates.
Pick-to: 6.5 6.2 5.15
Change-Id: I03666a4d9b0eac39ae97e150b4743120611a11b3
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
