If no TransferLog is given explicitly, decline to log.

This supports coexistence with other logging modules,
such as the custom one that UUNET uses.
Submitted by:	David J. MacKenzie <djm@va.pubnix.com>
Reviewed by:	Dean Gaudet, Brian Behlendorf, Randy Terbush


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@79015 13f79535-47bb-0310-9956-ffa450edef68