Infinite entry point redirection.

[ldez]

What does this PR do?

Prevent the creation of a redirection on the same entry point.

Motivation

Fixes #2925

Additional Notes

With those labels:

traefik.frontend.entryPoints=http,https
traefik.frontend.redirect.entryPoint=https

The current behavior;

http://foo:80 -> https://foo:433 -> https://foo -> https://foo:443 -> https://foo -> ...

Due to:

Creating frontend frontend-PathPrefix-foo-0  
Wiring frontend frontend-PathPrefix-foo-0 to entryPoint http 
Creating route route-frontend-PathPrefix-foo-0 PathPrefix:/foo 
Creating entry point redirect http -> https   # <-----------------------------------
Frontend frontend-PathPrefix-foo-0 redirect created 
Creating backend backend-whoami1             
Creating load-balancer wrr                   
Creating server server-upbeat_goldberg at http://172.17.0.2:80 with weight 0 
Wiring frontend frontend-PathPrefix-foo-0 to entryPoint https 
Creating route route-frontend-PathPrefix-foo-0 PathPrefix:/foo 
Creating entry point redirect https -> https   # <----------------------------------- 
Frontend frontend-PathPrefix-foo-0 redirect created 

[dtomcej]

Simple + Elegant
LGTM

[juliens]

LGTM

[nmengin]

LGTM