core: Fix TestContext2Apply_countDecreaseToOneCorrupted

We now include attribute changes in destroy diffs, so the expected output
of this test includes these changes.

Also includes a fix to legacyDiffComparisonString to actually sort the
attribute changes by name in the rendered diff.

terraform/context_test.go

@@ -945,6 +945,7 @@ func legacyDiffComparisonString(changes *plans.Changes) string {
 					keyLen = len(n)
 				}
 			}
+			sort.Strings(attrNamesOrder)
 
 			for _, attrK := range attrNamesOrder {
 				v := newAttrs[attrK]

terraform/terraform_test.go

@@ -474,6 +474,8 @@ const testTerraformApplyCountDecToOneCorruptedPlanStr = `
 DIFF:
 
 DESTROY: aws_instance.foo[0]
+  id:   "baz" => ""
+  type: "aws_instance" => ""