helper/schema: fix validating nested objects

When interpreting a nested object, we were validating against the "raw"
value, and not the interpolated value, causing incorrect errors.

This affects structures such as:

```tf
tags = "${list(map("foo", "bar"))}"
```

Prior to this, a complaint about "expected object, got string" since the
raw value is obviously a string, when the interpolated value is the
correct shape.

helper/schema/schema.go

@@ -1373,7 +1373,7 @@ func (m schemaMap) validateObject(
  k string,
  schema map[string]*Schema,
  c *terraform.ResourceConfig) ([]string, []error) {
- raw, _ := c.GetRaw(k)
+ raw, _ := c.Get(k)
  if _, ok := raw.(map[string]interface{}); !ok {
  return nil, []error{fmt.Errorf(
  "%s: expected object, got %s",

helper/schema/schema_test.go

@@ -3947,6 +3947,33 @@ func TestSchemaMap_Validate(t *testing.T) {
  Err: false,
  },
 
+ "Good sub-resource, interpolated value": {
+ Schema: map[string]*Schema{
+ "ingress": &Schema{
+ Type: TypeList,
+ Optional: true,
+ Elem: &Resource{
+ Schema: map[string]*Schema{
+ "from": &Schema{
+ Type: TypeInt,
+ Required: true,
+ },
+ },
+ },
+ },
+ },
+
+ Config: map[string]interface{}{
+ "ingress": []interface{}{
+ `${map("from", "80")}`,
+ },
+ },
+
+ Vars: map[string]string{},
+
+ Err: false,
+ },
+
  "Invalid/unknown field": {
  Schema: map[string]*Schema{
  "availability_zone": &Schema{