fix release dockerfile

Dockerfile

@@ -3,6 +3,7 @@ FROM golang
 ADD . /go/src/github.com/coreos/kube-etcd-controller
 
 RUN go get github.com/Masterminds/glide
+
 RUN cd /go/src/github.com/coreos/kube-etcd-controller && \
 	glide install && \
 	go build -o kube-etcd-controller ./cmd/controller/main.go && \