Fix envoy go build to use golang 1.10

Needed to fix etcd go get dependencies

Change-Id: I9bd75da7a2add899fce859cab68f1e7b853eb6ff
diff --git a/envoy/go/golang-builder/Dockerfile b/envoy/go/golang-builder/Dockerfile
index ae5ab59..de67a9d 100644
--- a/envoy/go/golang-builder/Dockerfile
+++ b/envoy/go/golang-builder/Dockerfile
@@ -1,4 +1,4 @@
-FROM golang:1.9.2
+FROM golang:1.10
 MAINTAINER Alex Peters <info@alexanderpeters.de>
 
 RUN apt-get update && apt-get install -y apt-transport-https ca-certificates jq curl gnupg2 software-properties-common