Switch to golang 1.5.4

Security fix for Go:
https://groups.google.com/forum/#!msg/golang-announce/9eqIHqaWvck/kXsfO0ogLAAJ

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

libnetwork/Dockerfile.build

@@ -1,4 +1,4 @@
-FROM golang:1.5.3
+FROM golang:1.5.4
 RUN apt-get update && apt-get -y install iptables
 
 RUN go get github.com/tools/godep \