Use OS::Heat::None for extra role BMC

The example's environments/base-extra-node.yaml
and environments/base-extra-node-all.yaml uses a
CentOS image to create undercloud like extra nodes.

There is no need for a virtual bmc for the servers
in this role. Set the BMC to OS::Heat::None so that
no BMC instance is created for this role.

Change-Id: I502de0a2e0352078e8f187cc0592f49ec0a9d65d

environments/base-extra-node-all.yaml

@@ -41,4 +41,5 @@ parameter_defaults:
   role: extra
 
 resource_registry:
+  OS::OVB::BMC: OS::Heat::None
   OS::OVB::BaremetalPorts: ../templates/baremetal-ports-extra-node-all.yaml

environments/base-extra-node.yaml

@@ -41,4 +41,5 @@ parameter_defaults:
   role: extra
 
 resource_registry:
+  OS::OVB::BMC: OS::Heat::None
   OS::OVB::BaremetalPorts: ../templates/baremetal-ports-extra-node.yaml

sample-env-generator/environments.yaml

@@ -76,12 +76,14 @@ environments:
       node_count: 1
     resource_registry:
       OS::OVB::BaremetalPorts: ../templates/baremetal-ports-extra-node.yaml
+      OS::OVB::BMC: OS::Heat::None
     children:
       -
         name: base-extra-node-all
         title: Base Configuration Options for Extra Nodes with All Ports Open
         resource_registry:
           OS::OVB::BaremetalPorts: ../templates/baremetal-ports-extra-node-all.yaml
+          OS::OVB::BMC: OS::Heat::None
   -
     name: all-networks
     title: Deploy with All Networks Enabled