Respect fallback cache keys for local cache

What does this MR do?

Fallback cache keys right now only work if a cache server is used. With local caches, they are ignored. This MR changes that.

Why was this MR needed?

The fallback_key is ignored if a local cache is used.

What's the best way to test this MR?

Add a fallback_key without having a cache server active.

What are the relevant issue numbers?

fixes: #27537 (closed)