Normalize data dir before rename on initialize failure (patroni#3374)

Close patroni#3371

Author: waynerv

patroni/postgresql/__init__.py

@@ -1357,7 +1357,7 @@ def move_data_directory(self) -> None:
                     os.unlink(source)
                     os.symlink(new_name, source)
 
-                new_name = '{0}.{1}'.format(self._data_dir, postfix)
+                new_name = '{0}.{1}'.format(self._data_dir.rstrip(os.sep), postfix)
                 logger.info('renaming data directory to %s', new_name)
                 if os.path.exists(new_name):
                     shutil.rmtree(new_name)