Fix lock tests #37 & #42 by properly calling our XML error response delegator.
Fix lock tests #37 & #42 by properly calling our XML error response delegator.

* subversion/libsvn_ra_serf/util.c
  (handle_response): Appropriately set up the error callbacks or use our
  defaults if there is no XML error response with a friendly message.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion