ra_serf: fix commit_tests 50. Handle a response with status code 409 as an error. Server returns 409 and a error message when a (pre-commit) hook has  failed.
ra_serf: fix commit_tests 50. Handle a response with status code 409 as an
error. Server returns 409 and a error message when a (pre-commit) hook has 
failed.

* subversion/libsvn_ra_serf/util.c
  (handle_response): Handle code 409 is an error response. Add some comments.

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