Cache lookups will immediately register a promise to prevent multiple requests for the same ressource

Use correct path for index.html for the memory lookup

Root cause: If multiple connections are opened at the same time after an update, the ui-middleware will do multiple requests to get initial data. That went especially worse, when e2e-tests are launched against ui-middlewares with multiple clients connecting at the same time.
Soltion: Make sure, that a node already caches stuff without a response.