[api-ref] Add network,subnet and FIP for cluster

Add API ref change for fixed-network, fixed-subnet and
floating_ip_enabled for cluster creation.

Task: 36326
Story: 2006208

Change-Id: I2724934de96de1a348d72bf39ff114e3f323eb9e

api-ref/source/clusters.inc

@@ -42,6 +42,9 @@ Request
   - master_flavor_id: master_flavor_id
   - labels: labels
   - flavor_id: flavor_id
+  - fixed_subnet: fixed_subnet
+  - fixed_network: fixed_network
+  - floating_ip_enabled: floating_ip_enabled_cluster
 
 .. note::
 

api-ref/source/parameters.yaml

@@ -283,6 +283,16 @@ floating_ip_enabled:
   in: body
   required: true
   type: boolean
+floating_ip_enabled_cluster:
+  description: |
+    Whether enable or not using the floating IP of cloud provider. Some
+    cloud providers used floating IP, some used public IP, thus Magnum
+    provide this option for specifying the choice of using floating IP.
+    If it's not set, the value of floating_ip_enabled in template
+    will be used.
+  in: body
+  required: false
+  type: boolean
 host:
   description: |
     The host for the service.