Fix flake8 H404 errors

Fix H404 error and start enforcing it.

Trivialfix

Change-Id: I0c062733660031faf43838798a697daf6674ef14
diff --git a/neutron_tempest_plugin/api/clients.py b/neutron_tempest_plugin/api/clients.py
index ee0289c..407e694 100644
--- a/neutron_tempest_plugin/api/clients.py
+++ b/neutron_tempest_plugin/api/clients.py
@@ -29,9 +29,7 @@
 
 
 class Manager(manager.Manager):
-    """
-    Top level manager for OpenStack tempest clients
-    """
+    """Top level manager for OpenStack tempest clients"""
     default_params = {
         'disable_ssl_certificate_validation':
             CONF.identity.disable_ssl_certificate_validation,