Merge r389697 and r390499 from trunk, making mod_disk_cache return better...

Merge r389697 and r390499 from trunk, making mod_disk_cache return better error codes, instead of a silly APR_EGENERAL.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@390598 13f79535-47bb-0310-9956-ffa450edef68