mod_socache_shmcb and mod_socache_dbm: finish support of

DefaultRuntimeDir

a partial conversion was made in r1299718, affecting cases
where no filename was specified


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1370225 13f79535-47bb-0310-9956-ffa450edef68