ra_serf: clean the cached realm string on the session after authentication  succeeded, so that we know when the server asks credentials the second time. 
ra_serf: clean the cached realm string on the session after authentication 
succeeded, so that we know when the server asks credentials the second time. 

Found by: Bert Huijben <b.huijben@competence.biz>

* subversion/libsvn_ra_serf/util.c
  (handle_response): reset realm string on session.

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