use provisioner attr defined in schema

terraform/context_apply_test.go

@@ -5183,7 +5183,7 @@ func TestContext2Apply_provisionerDestroyModule(t *testing.T) {
 	p.ApplyFn = testApplyFn
 	p.DiffFn = testDiffFn
 	pr.ApplyFn = func(rs *InstanceState, c *ResourceConfig) error {
-		val, ok := c.Config["foo"]
+		val, ok := c.Config["command"]
 		if !ok || val != "value" {
 			t.Fatalf("bad value for foo: %v %#v", val, c)
 		}

terraform/test-fixtures/apply-provisioner-destroy-module/child/main.tf

@@ -4,7 +4,7 @@ resource "aws_instance" "foo" {
     foo = "bar"
 
     provisioner "shell" {
-        foo  = "${var.key}"
+        command = "${var.key}"
         when = "destroy"
     }
 }