Refactor worker logic.

Worker logic is now moved to a new controller class. Add initial
support for new 'hpcs_action' and 'hpcs_response' JSON elements.
Drivers now have the option of supporting SUSPEND, ENABLE, DELETE
and UPDATE actions.

libra/worker/drivers/base.py

@@ -41,3 +41,15 @@ class LoadBalancerDriver(object):
     def activate(self):
         """ Activate any changes made. """
         raise NotImplementedError()
+
+    def suspend(self):
+        """ Suspend the load balancer. """
+        raise NotImplementedError()
+
+    def enable(self):
+        """ Enable a suspended load balancer. """
+        raise NotImplementedError()
+
+    def delete(self):
+        """ Delete a load balancer. """
+        raise NotImplementedError()