Fix issue #4306 'multiple editor drive file merges record wrong mergeinfo
during conflicts'.

* subversion/libsvn_client/merge.c
  (do_file_merge): If we can only perform a partial merge because a conflict
   broke the merge, then only record mergeinfo for that partial merge.  That
   was subsequent merges can finish the job.

* subversion/tests/cmdline/merge_tests.py
  (conflict_aborted_mergeinfo_described_partial_merge): Remove XFail
   decorator and tweak failure status comment.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1438683 13f79535-47bb-0310-9956-ffa450edef68