chore(rootfs/Dockerfile): update go toolchain to 1.10.3

See https://github.com/golang/go/issues?q=milestone%3AGo1.10.3

Author: mboersma

rootfs/Dockerfile

@@ -1,7 +1,7 @@
 FROM ubuntu:16.04
 
 ENV AZCLI_VERSION=2.0.30 \
-    GO_VERSION=1.10.2 \
+    GO_VERSION=1.10.3 \
     GLIDE_VERSION=v0.13.1 \
     GLIDE_HOME=/root \
     GOMETALINTER_VERSION=2.0.5 \