Make PUT with DAV_MODE_WRITE_TRUNC create a temporary file first and, when the

transfer has been completed successfully, move it over the old file.

Since this would break inode keyed locking, switch to filename keyed locking
exclusively.

PR: 39815
Submitted by: Paul Querna, Stefan Fritsch


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@834049 13f79535-47bb-0310-9956-ffa450edef68