refactor: only special case cnb for now

plugins/config/docker-args-deploy

@@ -14,9 +14,15 @@ trigger-config-docker-args() {
   STDIN=$(cat)
   trigger="$0 config_docker_args"
 
-  if ! is_image_herokuish_based "$IMAGE" "$APP" || is_image_cnb_based "$IMAGE"; then
+  if is_image_cnb_based "$IMAGE"; then
     ENV_ARGS="$(config_export app "$APP" --format docker-args-keys --merged)"
     echo -n "$STDIN $ENV_ARGS"
+    return
+  fi
+
+  if ! is_image_herokuish_based "$IMAGE" "$APP"; then
+    ENV_ARGS="$(config_export app "$APP" --format docker-args --merged)"
+    echo -n "$STDIN $ENV_ARGS"
   else
     echo -n "$STDIN"
   fi