Revised cluster action implementation
Revised cluster action implementation

Changes include:
1. renamed 'wait_for_action()' to '_wait_for_dependents()
2. Optimized status checking when waiting;
3. Included support for dependent action failure;
4. Return status with reason when return from waiting on dependents;
5. Added 'policy_data' to do_create(), do_delete() ... calls so that
   previous policy checking results can be passed in in a unified way.
6. Always return status with status_reaons from member methods;
7. Simplified return value checking in do_create();
8. Simplified return value checking in do_delete();
9. Added 'CLUSTER_ADD_NODES' action support;
10. Fixed incorrect call to schedule.action_timeout();
11. Renamed policies import to policy_mod
12. Dispatch action execution based on action name;
13. More precise error reporting for lock failures.

stackforge/senlin,openstack/senlin,tengqm/senlin-container,Alzon/senlin,tengqm/senlin,tengqm/senlin,openstack/senlin,Alzon/senlin,openstack/senlin,tengqm/senlin-container,stackforge/senlin