added default value for minPortsPerVM field at "google_compute_router…

…_nat" (GoogleCloudPlatform#9712)

* added default value for statis allocation

* setting the default from API

mmv1/products/compute/RouterNat.yaml

@@ -236,7 +236,8 @@ properties:
   - !ruby/object:Api::Type::Integer
     name: minPortsPerVm
     description: |
-      Minimum number of ports allocated to a VM from this NAT.
+      Minimum number of ports allocated to a VM from this NAT. Defaults to 64 for static port allocation and 32 dynamic port allocation if not set.
+    default_from_api: true
   - !ruby/object:Api::Type::Integer
     name: maxPortsPerVm
     description: |