Fixes #4974: AIX and unsupported OSes: failsafe.cf in initial-promises d...

...oesn't have a "execDate" variable, causing all reports to not contain the date/time
centos3 and 4, and redhat3 and 4 are already covered, about 6 lines higher up. The object of this pull request is not to address them, but to add the missing AIX support.