TRQ-2014. Fix a regression where the epilogue.parallel script would timeout every time it is run even if the script just exits. This is because interactive epilogues shouldn't attempt to open stdout and stderr, but they were changed to do so for epilogue.parallel scripts in 4.2.3. When they failed, instead of exiting the function returned, and it would follow the regular pbs_mom code until the parent killed it after a timeout. This change stops interactive epilogue.parallel scripts from attempting to open stdout/stderr and changes all child return statements to exit statements.