don't let mod_usertrack overwrite other cookies

PR: 26002
Submitted by: Scott Moore <apache nopdesign.com>
Reviewed by: Brad Nicholes, Jeff Trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@102450 13f79535-47bb-0310-9956-ffa450edef68