core: Fix TargetsTransformer tests

Resolution of dependencies automatically from expressions now requires
a schema to be available. To avoid the need to provide mock schemas for
all of these different resource types, we instead use the depends_on
argument here to mark the dependencies explicitly.

terraform/test-fixtures/transform-targets-basic/main.tf

@@ -1,16 +1,22 @@
 resource "aws_vpc" "me" {}
 
 resource "aws_subnet" "me" {
-  vpc_id = "${aws_vpc.me.id}"
+  depends_on = [
+    aws_vpc.me,
+  ]
 }
 
 resource "aws_instance" "me" {
-  subnet_id = "${aws_subnet.me.id}"
+  depends_on = [
+    aws_subnet.me,
+  ]
 }
 
 resource "aws_vpc" "notme" {}
 resource "aws_subnet" "notme" {}
 resource "aws_instance" "notme" {}
 resource "aws_instance" "notmeeither" {
-  name = "${aws_instance.me.id}"
+  depends_on = [
+    aws_instance.me,
+  ]
 }

terraform/test-fixtures/transform-targets-destroy/main.tf

@@ -1,18 +1,26 @@
 resource "aws_vpc" "notme" {}
 
 resource "aws_subnet" "notme" {
-  vpc_id = "${aws_vpc.notme.id}"
+  depends_on = [
+    aws_vpc.notme,
+  ]
 }
 
 resource "aws_instance" "me" {
-  subnet_id = "${aws_subnet.notme.id}"
+  depends_on = [
+    aws_subnet.notme,
+  ]
 }
 
 resource "aws_instance" "notme" {}
 resource "aws_instance" "metoo" {
-  name = "${aws_instance.me.id}"
+  depends_on = [
+    aws_instance.me,
+  ]
 }
 
 resource "aws_elb" "me" {
-  instances = "${aws_instance.me.*.id}"
+  depends_on = [
+    aws_instance.me,
+  ]
 }