Add available params in subnets client's comment

Some interfaces in subnets client have **kwargs parameter, but no api
reference links are given. so this is to add "Available params" in their
comments.

Change-Id: I770cf5cce2c532b914db74742bc86629db43ae60
diff --git a/tempest/lib/services/network/subnets_client.py b/tempest/lib/services/network/subnets_client.py
old mode 100644
new mode 100755
index 63ed13e..9de4a33
--- a/tempest/lib/services/network/subnets_client.py
+++ b/tempest/lib/services/network/subnets_client.py
@@ -16,11 +16,21 @@
 class SubnetsClient(base.BaseNetworkClient):
 
     def create_subnet(self, **kwargs):
+        """Creates a subnet on a network.
+
+        Available params: see http://developer.openstack.org/
+                              api-ref-networking-v2.html#createSubnet
+        """
         uri = '/subnets'
         post_data = {'subnet': kwargs}
         return self.create_resource(uri, post_data)
 
     def update_subnet(self, subnet_id, **kwargs):
+        """Updates a subnet.
+
+        Available params: see http://developer.openstack.org/
+                              api-ref-networking-v2.html#updateSubnet
+        """
         uri = '/subnets/%s' % subnet_id
         post_data = {'subnet': kwargs}
         return self.update_resource(uri, post_data)