Small fix to net test add-on context expansion (#2828)

* Small fix to net test add-on context expansion

* linting

fast/addons/2-networking-test/README.md

@@ -112,4 +112,5 @@ terraform apply
 |---|---|:---:|---|
 | [instance_addresses](outputs.tf#L17) | Instance names and addresses. |  |  |
 | [instance_ssh](outputs.tf#L24) | Instance SSH commands. |  |  |
+| [service_account_emails](outputs.tf#L33) | Service account emails. |  |  |
 <!-- END TFDOC -->

fast/addons/2-networking-test/context.tf

@@ -38,7 +38,8 @@ locals {
   # recompose subnet ids checking for context substitutions
   _subnets = {
     for k, v in local._subnet_attrs : k => merge(v, v.region_alias == null ? {} : {
-      id = try(replace(v.id, v.region, v.region_alias))
+      id     = try(replace(v.id, v.region, v.region_alias))
+      region = coalesce(v.region_alias, v.region)
     })
   }
   # derive product of instances and zones and expand instance contexts
@@ -52,7 +53,7 @@ locals {
           var.subnet_self_links[v.network_id][local._subnets[v.subnet_id].id],
           v.subnet_id
         )
-        zone = "${local._subnets[v.subnet_id].region}-${z}"
+        zone = "${local._subnets[v.subnet_id].region_alias}-${z}"
       })
     ]
   ])

fast/addons/2-networking-test/outputs.tf

@@ -29,3 +29,10 @@ output "instance_ssh" {
     )
   }
 }
+
+output "service_account_emails" {
+  description = "Service account emails."
+  value = {
+    for k, v in module.service-accounts : k => v.email
+  }
+}