Fix brain-o in parsing base-64-encoded propvals.

* libsvn_ra_dav/fetch.c (end_element):  send the *decoded* propval
  into the editor, not the original value.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/issue-1429-dev@847794 13f79535-47bb-0310-9956-ffa450edef68