Let the svndumpfilter_tests.py tests see the stderr results when running svndumpfilter in non-quiet mode.
Let the svndumpfilter_tests.py tests see the stderr results when running
svndumpfilter in non-quiet mode.

* subversion/tests/cmdline/svndumpfilter_tests.py

  (filter_and_return_output): Return stderr.

  (reflect_dropped_renumbered_revs,
   svndumpfilter_loses_mergeinfo,
   _simple_dumpfilter_test,
   filter_mergeinfo_revs_outside_of_dump_stream): Update callers of
   filter_and_return_output.

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