mod_cache: Fix uninitialized tmppath variable.

PR: 54949
Submitted by: <jkaluza redhat.com>
Reviewed by: minfrin, trawick, wrowe



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1497099 13f79535-47bb-0310-9956-ffa450edef68