services/vrrp/manager.py: fix bug in list_request_handler()

  File "ryu/services/vrrp/manager.py", line 153, in list_request_handler
    instance.interface)]
TypeError: __init__() takes exactly 5 arguments (4 given)
lib/rpc.py: fix assertion in create_request and create_notification
services/vrrp: create rpc_param.py
services/vrrp/rpc_manager.py: cleanup
tests/vrrp/rpc_client_interactive.py: cleanup
services/vrrp/event.py pep8