Previously trying to execute a test function with an unknown data tag
would print an error message but exit with 0.
This patch stores a test failure, and continues trying to execute the
rest of the command line arguments, if any. In the end the process exits
with the usual exit code (number of failed tests) which is now !=0.
Pick-to: 6.4 6.3 6.2
Fixes: QTBUG-24240
Change-Id: Id4d422035f173e01e77ca88028dfd94dc0f9085c
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
d23dcc0542