Pull the deploying app image name where necessary

All of these commands should execute against the image that is in use versus the "latest" that dokku provides the system with.

plugins/config/docker-args-deploy

@@ -6,7 +6,7 @@ source "$PLUGIN_AVAILABLE_PATH/config/functions"
 config_docker_args() {
   declare desc="config docker-args plugin trigger"
   local trigger="$0 config_docker_args"
-  local STDIN=$(cat); local APP="$1"; local IMAGE_TAG="$2"; local IMAGE=$(get_app_image_name "$APP" "$IMAGE_TAG")
+  local STDIN=$(cat); local APP="$1"; local IMAGE_TAG="$2"; local IMAGE=$(get_deploying_app_image_name "$APP" "$IMAGE_TAG")
   local DOCKERFILE_ENV_FILE="$DOKKU_ROOT/$APP/DOCKERFILE_ENV_FILE"
   verify_app_name "$APP"