Fix handle_create() of senlin cluster resource
Fix handle_create() of senlin cluster resource

The change I272fbace441db76339bb6fb689e7f863cca49cad
merged, some nits to be fixed in this patch:
1. redundant 'action' definition in handle_create()
2. give the default value [] for 'policies' properties
3. no need to get cluster info when get attribute
   'policies'.

Change-Id: Ibcca31b59b3486a65a16538b571d29a12b158060

openstack/heat,openstack/heat,noironetworks/heat,noironetworks/heat