use QTRY_VERIFY instead of qWait() in tst_QDialog::reject()
use QTRY_VERIFY instead of qWait() in tst_QDialog::reject()

This test already uses qWaitForWindowManager(), but on X11, reshowing
a dialog can take long as the window manager has to do more work
before remapping the window. we should give it more time (hence the
change to QTRY_VERIFY)

Reviewed-by: Rohan McGovern
(cherry picked from commit d763b9a56c5f488a6a4187f6aa454405ab75d09b)

pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,radekp/qt,radekp/qt,radekp/qt,igor-sfdc/qt-wk,radekp/qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,radekp/qt,igor-sfdc/qt-wk,radekp/qt,radekp/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,radekp/qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,radekp/qt,radekp/qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt