SyslogAuditLogHandlerAddHandler and FileAuditLogHandlerAddHandler are doing reference validation directly in populateModel. This should instead be done in a separate step, removing the requirement to have the add op for the formatter occur before the add op for the handler, so long as both ops occur within the set of ops handled by the same OperationContext.

This will simplify booting from a filesystem tree instead of xml, removing the need to persist ordering information about formatter/handler in the FS.