Merge r1677462 from trunk.

mod_dav: Avoid doing the walk on a COPY source for handling preconditions if
there are no preconditions provided.

* modules/dav/main/util.c:
  (dav_validate_request): avoid validating locks and ETags when there are
    no If headers providing them on a resource we aren't modifying.

Committed by: breser
Reviewed by: breser, ylavic, rjung
Backported by: ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1678710 13f79535-47bb-0310-9956-ffa450edef68