Check grace_period before use it
Check grace_period before use it

CLUSTER_SCALE_IN action can be attached by deletion policy and
scaling policy, but action data is different.
Deletion policy's action data:
{"deletion":
     { "candidates": [],
       "grace_period": 20,
       "destroy_before_deletion": False}
}
Scaling policy's action data:
{"deletion": {"count": 2}}

Change-Id: I2dd9dbec2fbfb08eb6c41e4552d91ed84550ab49

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