Make the behavior when we cannot write to a log or audit file

Make the behavior when we cannot write to a log or audit file
configurable.  File log failures are ignored by default for consistency
with syslog.  Audit errors are ignored by default to allow the admin
to fix the issue.  I/O log file errors are still fatal by default
since if I/O logging is activated it is usually to have an audit trail.
Bug #751