Make add_dhcp_agent_to_network  use **kwargs

As we discussed on
http://lists.openstack.org/pipermail/openstack-dev/2015-July/068864.html
All http POST/PUT methods need to contain **kwargs as their arguments.

This patch makes add_dhcp_agent_to_network of network_client.py
use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: I358b96723a97070673a6020994c082fbd6c1cfe7
diff --git a/tempest/api/network/admin/test_dhcp_agent_scheduler.py b/tempest/api/network/admin/test_dhcp_agent_scheduler.py
index 7692b56..f186b36 100644
--- a/tempest/api/network/admin/test_dhcp_agent_scheduler.py
+++ b/tempest/api/network/admin/test_dhcp_agent_scheduler.py
@@ -92,6 +92,6 @@
 
     def _add_dhcp_agent_to_network(self, network_id, agent):
         self.admin_client.add_dhcp_agent_to_network(agent['id'],
-                                                    network_id)
+                                                    network_id=network_id)
         self.assertTrue(self._check_network_in_dhcp_agent(
             network_id, agent))
diff --git a/tempest/services/network/json/network_client.py b/tempest/services/network/json/network_client.py
index 08316be..7d82232 100644
--- a/tempest/services/network/json/network_client.py
+++ b/tempest/services/network/json/network_client.py
@@ -325,10 +325,13 @@
         }
         return self.update_resource(uri, put_body)
 
-    def add_dhcp_agent_to_network(self, agent_id, network_id):
-        post_body = {'network_id': network_id}
+    def add_dhcp_agent_to_network(self, agent_id, **kwargs):
+        # TODO(piyush): Current api-site doesn't contain this API description.
+        # After fixing the api-site, we need to fix here also for putting the
+        # link to api-site.
+        # LP: https://bugs.launchpad.net/openstack-api-site/+bug/1526212
         uri = '/agents/%s/dhcp-networks' % agent_id
-        return self.create_resource(uri, post_body)
+        return self.create_resource(uri, kwargs)
 
     def list_subnetpools(self, **filters):
         uri = '/subnetpools'