Connect Envoy: Intentions not working on L4 Traffic

#### Intentions not Working with Envoy Proxy on L4 Traffic

#### What I am doing when this happend?

- Consul v1.6.2 and Envoy v1.11.1

- Couter Service

A HTTP Server written in Python, accept PUT request for adding counts, accept GET requests for getting counts. [src](https://github.com/VitoVan/demo-service-counter/blob/85b9eb3282b65a044e03d8248ba59cee81803d2b/server.py)

- Timer Service

A HTTP Server emulated by `nc -l -s 0.0.0.0 -p 80`, simply reply the time and IP no matter what/how you send to that port. [src](https://github.com/VitoVan/demo-service-timer/blob/aa762545c76165851d1554650d9233f6160b27bc/server.sh)

- Dashboard Service

A Nginx instance with a static HTML and configured with 2 upstreams connect to 127.0.0.1 8080 and 8081, which will be provided by Sidecar. [src](https://github.com/VitoVan/demo-service-dashboard/blob/8600ca790b79efe4a1588e553ac32cdad3c7fdcf/nginx.conf)

#### What I have done caused this happen?

For the Sidecars, they worked very well, then I tried to create Intentions.

- First, `deny` from `dashboard` to `counter`, the time I created the intention, the dashboard lost the connection to counter, this worked as my wish.

- Second, `deny` from `dashboard` to `timer`, after I created the intention, nothing happened. The timer keeps refreshing, this intention does not work.

I checked the consul log, it indeed said something about denying access from `dashboard` to `timer`, but what actually happening is it is not denied.

#### What I have done after this happened?

- First, I stoped the Envoy based timer-sidecar-proxy, and start another one with Consul Native Proxy, intentions worked fine.

- Second, I switch back to the Envoy based timer-sidecar-proxy, then modified the source code of timer service, use Python for a standard HTTP implementation ([src](https://github.com/VitoVan/demo-service-timer/blob/15ecebe664c654a3dccacd40bfd8ae6d01a2ad87/server.py)). This time, Intentions with Envoy Proxy works fine.

- Third, I also tried Envoy Proxy with Redis, intentions not working.

#### Question

Are Intentions NOT supposed to work when use Envoy integration on L4 or "Bad Implemented HTTP"?

Thanks in advance, for your great work on Consul.