Reject certificate error for non-overridable errors

On certificate validation error page load is just halted
meaning that no progress or load result are reported and
no default error page for certificate errors is shown.
Even though documentation states that 'By default,
an invalid certificate will be automatically rejected' and
that aligns with default implementation of certificateError
method within Page and non-deferred errors in quick View,
page or view silently stays in an intermediate state
for non-overridable errors. Fix this inconsistent behavior
by automatically rejecting certificate for every invalid case
(non-overridable error, not deferred or not implemented
overridable method).

Change-Id: Id1cee2ee5cc45bdcb5f262a6c99c84274e6ca374
Reviewed-by: Jüri Valdmann <juri.valdmann@qt.io>