Don't duplicate external/private_net param

There's no need for these to be specified in the
create-private-network environment since they're a mandatory part
of the base environment.

environments/create-private-network.yaml

@@ -13,16 +13,6 @@ parameter_defaults:
   # Type: comma_delimited_list
   dns_nameservers: ['8.8.8.8']
 
-  # An external network for the private network to route to
-  # Mandatory. This parameter must be set by the user.
-  # Type: string
-  external_net: <None>
-
-  # Name of private network
-  # Mandatory. This parameter must be set by the user.
-  # Type: string
-  private_net: <None>
-
   # CIDR for private network subnet
   # Type: string
   private_net_cidr: 10.0.1.0/24

sample-env-generator/environments.yaml

@@ -108,7 +108,9 @@ environments:
       existing one.
     files:
       templates/private-net-create.yaml:
-        parameters: all
+        parameters:
+          - dns_nameservers
+          - private_net_cidr
     resource_registry:
       OS::OVB::PrivateNetwork: ../templates/private-net-create.yaml
   -