make 'make lint' run gocyclo (again)

build/Dockerfile

@@ -1,7 +1,7 @@
 FROM golang:1.5.2
 ENV GO15VENDOREXPERIMENT 1
 RUN apt-get update && apt-get install -y libpcap-dev python-requests time
-RUN go get github.com/golang/lint/golint
+RUN go get github.com/golang/lint/golint github.com/fzipp/gocyclo
 RUN go clean -i net && go install -tags netgo std
 RUN go install -race -tags netgo std
 COPY build.sh /