Fix assertion on checkout from pre-1.8 server over ra_serf with 
http-bulk-updates=off.

* subversion/libsvn_ra_serf/update.c
  (open_updated_file): Do not walk through file properties. They can be 
   not fetched yet.
  (close_updated_file): Walk through file properties here.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1468439 13f79535-47bb-0310-9956-ffa450edef68