Fix failing merge test with Ev2 by using UnorderedOutput.
Fix failing merge test with Ev2 by using UnorderedOutput.

Current number of failing Ev2 tests: 4

* subversion/tests/cmdline/merge_tests.py
  (merge_range_prior_to_rename_source_existence): Don't rely on output ordering.

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