Add support for proxy protocol decoding and encoding in TCP services

[jbguerraz]

Examples:

apiVersion: v1
data:
  "9000": default/http-svc:80:PROXY:PROXY
kind: ConfigMap
metadata:
  name: ingress-controller-tcp
  namespace: kube-system

# TCP services
+    upstream tcp-default-http-svc-80 {
+        server                  172.17.0.3:8080;
+        server                  172.17.0.4:8080;
+    }
+
+    server {
+        listen                  9000 proxy_protocol;
+        listen                  [::]:9000 proxy_protocol;
+        proxy_pass        tcp-default-http-svc-80;
+        proxy_protocol   on;
+    }

apiVersion: v1
data:
  "9000": default/http-svc:80::PROXY
kind: ConfigMap
metadata:
  name: ingress-controller-tcp
  namespace: kube-system

 # TCP services
+    upstream tcp-default-http-svc-80 {
+        server                  172.17.0.3:8080;
+        server                  172.17.0.4:8080;
+    }
+
+    server {
+        listen                  9000;
+        listen                  [::]:9000;
+        proxy_pass        tcp-default-http-svc-80;
+        proxy_protocol   on;
+    }

apiVersion: v1
data:
  "9000": default/http-svc:80:PROXY
kind: ConfigMap
metadata:
  name: ingress-controller-tcp
  namespace: kube-system

# TCP services
+    upstream tcp-default-http-svc-80 {
+        server                  172.17.0.3:8080;
+        server                  172.17.0.4:8080;
+    }
+
+    server {
+        listen                  9000 proxy_protocol;
+        listen                  [::]:9000 proxy_protocol;
+        proxy_pass        tcp-default-http-svc-80;
+    }

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[k8s-reviewable]

This change is 

[coveralls]

Coverage increased (+0.01%) to 43.742% when pulling a24d657 on skilld-labs:proxy-protocol-tcp-upstream into 6e24dc6 on kubernetes:master.

[aledbf]

/lgtm

[aledbf]

@jbguerraz thanks!

[jbguerraz]

@aledbf you're welcome ! Thank you !