Fixed mod_auth_digest.c: result of an open() call was being

checked against the wrong failure value.

Submitted by: Rick Ohnemus <rjohnemus@systemware-inc.com>
Reviewed by: Ralf S. Engelschall
PR: 5292


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@84174 13f79535-47bb-0310-9956-ffa450edef68