Fix syntax issue when modifying vpc attributes

cloudbridge/providers/aws/services.py

@@ -966,7 +966,7 @@ class AWSNetworkService(BaseNetworkService):
         if label:
             cb_net.label = label
         self.provider.ec2_conn.meta.client.modify_vpc_attribute(
-            VpcId=cb_net.id, EnableDnsHostnames=True)
+            VpcId=cb_net.id, EnableDnsHostnames={'Value': True})
         return cb_net
 
     @dispatch(event="provider.networking.networks.delete",