To complete the issue #3314 'DAV can overwrite directories during copy' work
ask mod_dav explicitly not to overwrite existing resources.

* subversion/libsvn_ra_serf/commit.c
  (setup_copy_file_headers): Remove unneeded depth header and ask for
    overwrites to 'F'ail.
  (setup_copy_dir_headers): Ask for overwrites to 'F'ail.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1553552 13f79535-47bb-0310-9956-ffa450edef68