expand a merge_tests.py 43 to cover reopened issue #2821.
expand a merge_tests.py 43 to cover reopened issue #2821.

* subversion/tests/cmdline/merge_tests.py
  (avoid_repeated_merge_on_subtree_with_merge_info):  expand to cover problem
  with subtree merges described here:
  http://subversion.tigris.org/issues/show_bug.cgi?id=2821#desc22.
  (test_list): Mark avoid_repeated_merge_on_subtree_with_merge_info as XFail.

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