chore(e2e): Fix availability zone check (#5935)

enos/modules/aws_az_finder/main.tf

@@ -16,14 +16,20 @@ variable "instance_type" {
 }
 
 data "aws_ec2_instance_type_offerings" "infra" {
+  for_each = toset(var.instance_type)
   filter {
     name   = "instance-type"
-    values = var.instance_type
+    values = [each.key]
   }
 
   location_type = "availability-zone"
 }
 
-output "availability_zones" {
-  value = data.aws_ec2_instance_type_offerings.infra.locations
+locals {
+  az_sets    = [for d in data.aws_ec2_instance_type_offerings.infra : toset(d.locations)]
+  common_azs = length(local.az_sets) > 0 ? setintersection(local.az_sets...) : []
+}
+
+output "availability_zones" {
+  value = local.common_azs
 }