QSslCertificate: also check common name for blacklisted certificates

QSslCertificate: also check common name for blacklisted certificates

... to reduce the possibility of blacklisting valid certificates that
happen to have the same serial number as a blacklisted one, which is
unlikely, but possible.

Reviewed-by: Richard J. Moore <rich@kde.org>
(cherry picked from commit 6b1a8129623e3716f2fc075608b260ce7c381fe2
and adapted to the source incompatible change)

Change-Id: If714c34f6ce028032eee6d68f34d088b6ad5a0cc
Reviewed-on: http://codereview.qt.nokia.com/3895
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Peter Hartmann <peter.hartmann@nokia.com>