Part 1 of plural ports: Add protocol to Endpoints

This makes it easier to make the second step, which is moving endpoints
to a struct instead of a string.

pkg/master/publish.go

@@ -135,6 +135,7 @@ func (m *Master) ensureEndpointsContain(serviceName string, endpoint string) err
 				Name:      serviceName,
 				Namespace: api.NamespaceDefault,
 			},
+			Protocol: "TCP",
 		}
 	}
 	found := false