Expand test for issue #3324 to cover reverse merge scenario.
Expand test for issue #3324 to cover reverse merge scenario.

* subversion/tests/cmdline/merge_tests.py
  (merge_range_prior_to_rename_source_existence): Make a second branch on
   which to demonstrate issue #3324 but during a reverse merge.  Any fix 
   for this issue needs to work for both!

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