Standardize the way in which we set variables

plugins/00_dokku-standard/pre-delete

@@ -1,9 +1,7 @@
 #!/usr/bin/env bash
 set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 
-APP="$1"
-IMAGE=dokku/"$1"
-CACHE_DIR="$DOKKU_ROOT/$APP/cache"
+APP="$1"; IMAGE="dokku/$APP"; CACHE_DIR="$DOKKU_ROOT/$APP/cache"
 
 docker run -v $CACHE_DIR:/cache $IMAGE find /cache -depth -mindepth 1 -maxdepth 1 -exec rm -Rf {} \;