ra_serf: Handle authentication challenges when we issue MKACTIVITY request.
ra_serf: Handle authentication challenges when we issue MKACTIVITY request.

* subversion/libsvn_ra_serf/commit.c
  (mkactivity_context_t): Remove unneeded fields folded into handler struct.
  (handle_status_only): Disregard possibly erroneous status message.
  (setup_mkactivity): Remove.
  (open_root): Create handler structure and call svn_ra_serf__request_create();
  don't set the log message in the root dir's property hashes but use a
  separate hash instead for revprops.

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