Issue
When defining same service entry as existing one, a new is created instead of acknowledging that it exists.
In addition this breaks use on the service entry.

How to reproduce
1. If I create a ServiceEntry with the host "www.redhat.com" and port number, protocol, name : 443, HTTPS, https
An Envoy Listener with the following VIP is created : 240.240.0.1
I can curl the following URL : "https://www.redhat.com", the VIP used to establish the connection is 240.240.0.1

2. If I create another ServiceEntry with the host "www.redhat.com" and port number, protocol, name : 80, HTTP, http
An Envoy Listener with the following VIP is created : 240.240.0.2
I can curl the following URL : http://www.redhat.com", the VIP used to establish the connection is 240.240.0.2
I CAN'T ANYMORE curl the following URL : "https://www.redhat.com", the VIP used to establish the connection is 240.240.0.2. So the one associated with the HTTP protocol.

Expected behavior:

• when defining two service entry in the same namespace, both should be reachable
• when defining an already existing service entry, system should not create new one