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

PR: 54145

Submitted by: Ben Reser <ben reser.org>
Reviewed by: trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1464241 13f79535-47bb-0310-9956-ffa450edef68