disable storybook on frontend only setup as well if configured as such

mprocs.yaml

@@ -16,4 +16,8 @@ procs:
   storybook:
     cwd: <CONFIG_DIR>/holi-frontends
     shell: >
-      yarn storybook:dev --no-open
+      if [ "$LOCAL_BACKEND_STORYBOOK" = "true" ]; then
+        ./mprocs-start-storybook.sh;
+      else
+        echo "Not starting local Storybook because LOCAL_BACKEND_STORYBOOK is not set to 'true'";
+      fi