X-Consul-Index value times out when using it in request

#### Overview of the Issue

I have set up an instance of Consul v1.14.6. Whenever I do a request like `http://XX.XX.XX:8500/v1/kv/core/?recurse` I obtain the value of `x-consul-index` being `4653482`.
Later on, I do a request such as `http://XX.XX.XX:8500/v1/kv/core/?recurse&wait=10000s&index=4653482` Meaning I use the same value from `x-consul-index` and the request times out whilst if I use a total different value, it works just fine.

Start at Consul's HTTP KV API handling for /v1/kv/core/?recurse, focusing on how the X-Consul-Index response header is consumed by the index and wait query parameters. Reproduce the two requests against Consul v1.14.6, then trace the blocking-query behavior and add or update coverage so the same returned index has a defined, verified outcome.

Written by the indexing model from the issue text.