Bump Go to 1.9.3

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libnetwork/Dockerfile.build

@@ -1,4 +1,4 @@
-FROM golang:1.8.5
+FROM golang:1.9.3
 RUN apt-get update && apt-get -y install iptables
 
 RUN go get github.com/tools/godep \