Prevent XFail of new test in r25204 from failing subsequent tests.
Prevent XFail of new test in r25204 from failing subsequent tests.

* subversion/tests/cmdline/merge_tests.py
  (copy_src_detection_bug_if_target_has_many_ancestors_in_same_commit): Move
  os.chdir()s inside our 'standard' try/finally blocks.

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