tf: use_lockfile

Author: sorah

tf/backend.tf

@@ -1,8 +1,8 @@
 terraform {
   backend "s3" {
-    bucket         = "rk-infra"
-    region         = "ap-northeast-1"
-    key            = "terraform/rko-router.tfstate"
-    dynamodb_table = "rk-terraform"
+    bucket       = "rk-infra"
+    region       = "ap-northeast-1"
+    key          = "terraform/rko-router.tfstate"
+    use_lockfile = true
   }
 }