test_alternate_config_datadir: generate config file that can be parsed on Python 3

The config file generated and used on this test was missing a
separator between the section name and the first key/value line.

This adds a new line and makes the resulting file aesthetically
pleasing and able to be parsed.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

selftests/functional/test_basic.py

@@ -184,7 +184,7 @@ class RunnerOperationTest(unittest.TestCase):
                    'test_dir': os.path.join(base_dir, 'test'),
                    'data_dir': os.path.join(base_dir, 'data'),
                    'logs_dir': os.path.join(base_dir, 'logs')}
-        config = '[datadir.paths]'
+        config = '[datadir.paths]\n'
         for key, value in iteritems(mapping):
             if not os.path.isdir(value):
                 os.mkdir(value)