Sync test suite with upstream

Sync test suite with upstream

* tests@1000230: (31 commits)
  Add NODES support to the testsuite.
  Import test data from svnsync_tests_data after converting the dumpfile to v3.
  svnrdump: Fix normalization of propstrings in dumper.
  Import test data from svnsync_tests_data after converting the dumpfile to v3.
  svnrdump: Import a couple of test data files involving tagging the trunk.
  svnrdump: Fix loader's usage of open_directory.
  svnrdump: Fix dumping directory properties from a previous revision.
  load_editor: Fix code that recursively walks directories to find a path.
  dump_editor (delete_entry): Duplicate key before entering it in the hashtable.
  svnrdump: Mark tests that fail conditionally on ra_dav as WIP for buildbot.
  dump_editor: Fix data corruption in deleted_entries hashtable.
  Import test data from svnsync_tests_data after converting the dumpfile to v3.
  Import test data from svnsync_tests_data after converting the dumpfile to v3.
  dump_editor (dump_node): Handle `path` or `copyfrom_path` of "/" correctly.
  Import test data from svnsync_tests_data after converting the dumpfile to v3.
  svnrdump_tests.py: Explain mismatched_headers_re.
  svntest (ExpectedOutput.matches_except): Wrap string in an Exception object.
  Import test data from svnsync_tests_data after converting the dumpfile to v3.
  Import test data from svnsync_tests_data after converting the dumpfile to v3.
  Import test data from svnsync_tests_data after converting the dumpfile to v3.
  ...