Fix passing section argument into the set_service_setting

`_set_rate_limiting_config` was attempting to pass `section` value
by position but its position was off and the `service` argument
was getting passed instead. This caused bad formatting in the
crudini command and subsequent .conf file. This can be see in the
tempest log [1]

To prevent this from happening in the future. I am passing arguments
by their names.
I also put the  metada_rate_limiting string literal into a constant
to keep the code DRY.

[1] https://paste.opendev.org/show/btVjyzKuNaiI8UC1NC9M/

Related: https://issues.redhat.com/browse/OSPRH-9569

Change-Id: Ic73def44d03fb28b5975c1d96a471e0463d01740

whitebox_neutron_tempest_plugin/tests/scenario/test_metadata_rate_limiting.py

@@ -27,6 +27,7 @@ from whitebox_neutron_tempest_plugin.tests.scenario import base as wb_base
 CONF = config.CONF
 WB_CONF = CONF.whitebox_neutron_plugin_options
 LOG = log.getLogger(__name__)
+METADATA_RATE_LIMITING_SECTION = 'metadata_rate_limiting'
 
 
 class TestMetadataRateLimiting(wb_base.BaseTempestWhiteboxTestCase):
@@ -93,14 +94,15 @@ class TestMetadataRateLimiting(wb_base.BaseTempestWhiteboxTestCase):
                 LOG.debug(
                     'Setting metadata rate limiting configuration:\n'
                     f'File - {cls.metadata_conf_file}\n'
-                    'Section - metadata_rate_limiting\n'
+                    f'Section - {METADATA_RATE_LIMITING_SECTION}\n'
                     f'Parameter - {key}\n'
                     f'Value - {value}\n')
                 cls.set_service_setting(
-                    'compute',
-                    cls.metadata_conf_file,
-                    'metadata_rate_limiting',
-                    key, value)
+                    node_type='compute',
+                    file=cls.metadata_conf_file,
+                    section=METADATA_RATE_LIMITING_SECTION,
+                    param=key,
+                    value=value)
         cls._restart_metadata_agent()
 
     def tearDown(self):
@@ -121,7 +123,7 @@ class TestMetadataRateLimiting(wb_base.BaseTempestWhiteboxTestCase):
         cls.run_group_cmd(
             'sudo crudini --del {} {} && sudo sync'.format(
                 cls.metadata_conf_file,
-                'metadata_rate_limiting'),
+                METADATA_RATE_LIMITING_SECTION),
             'compute')
 
     @classmethod