Werk #3139: fixed a couple of minor issues in call to notification scripts

The fixed issues are as follows: - in case of a timeout of the notification script, the script is supposed to be terminated. This worked only on python 2.6 and newer - due to timing there was a good chance the exit code of the notification script was ignored - the output of the notification script was buffered in memory until the process exited before being written. Theoretically this could cause high memory usage in the notification processes

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