mod_dav: Improve error handling in dav_method_put(), add new

dav_join_error() function.  PR 54145.

trunk patch: http://svn.apache.org/r1464241
2.4.x patch: http://people.apache.org/~minfrin/httpd-mod_dav-errorhandling.patch
Submitted by: Ben Reser <ben reser.org>
Reviewed by: minfrin, jim, jorton


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1486464 13f79535-47bb-0310-9956-ffa450edef68