Merge r1735906 from trunk:

Avoid a call to 'prep_walk_cache' if possible, just as in 'ap_if_walk' and 'ap_location_walk'
Submitted by: jailletc36
Reviewed by: jailletc36, jim, ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1800267 13f79535-47bb-0310-9956-ffa450edef68