Fixes#12048Fixes#12319
Regression introduced in #11693
Local reproduction steps:
1. `consul agent -dev`
2. `curl -sLiv 'localhost:8500/v1/agent/connect/ca/leaf/web'`
3. make note of the `X-Consul-Index` header returned
4. `curl -sLi 'localhost:8500/v1/agent/connect/ca/leaf/web?index=<VALUE_FROM_STEP_3>'`
5. Kill the above curl when it hangs with Ctrl-C
6. Repeat (2) and it should not hang.