tests: fixing bootstrap code and invalid instance

- bootstrap code was not correctly instantiating the cloud function.
- compute_instance has a typo from a previous commit.
- re-disabling forwarding rule as it still has the backend_service
  fingerprint requirement

tests/integration/targets/gcp_compute_forwarding_rule/aliases

@@ -1 +1,2 @@
 cloud/gcp
+unsupported

tests/integration/targets/gcp_compute_instance/tasks/autogen.yml

@@ -80,7 +80,7 @@
       boot: 'true'
       source: "{{ disk }}"
     - auto_delete: 'true'
-      interface: SCS
+      interface: NVME
       type: SCRATCH
       initialize_params:
         disk_type: local-ssd