Add proper readiness probe

Also remove liveness one as it does nothing

Change-Id: Ifefd87046db04690bd9ae2ada3cef8eb616aa584

service/horizon.yaml

@@ -6,10 +6,10 @@ service:
     - name: horizon
       image: horizon
       probes:
-        readiness: "true"
-        liveness:
-          command: "true"
-          type: "exec"
+        readiness:
+          type: "httpGet"
+          port: {{ horizon.port.cont }}
+          path: "/"
       volumes:
         - name: horizon-logs
           path: "/var/log/ccp/horizon"