Separate waitForStarted() and waitForFinished() to properly
catch startup errors and kill hanging processes. Also check
exit status and code.
Task-number: PYSIDE-855
Change-Id: Ic8e623f4a8c716a2892767a8dbc06ba4ffb90b5a
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>