don't embed docker binary

We needed it because some of our invocations of Weave Net's `weave`
script depended on it, but that is no longer the case as of Weave Net
2.1.

Fixes #2974.

Makefile

@@ -12,9 +12,6 @@ SCOPE_BACKEND_BUILD_IMAGE=$(DOCKERHUB_USER)/scope-backend-build
 SCOPE_BACKEND_BUILD_UPTODATE=.scope_backend_build.uptodate
 SCOPE_VERSION=$(shell git rev-parse --short HEAD)
 WEAVENET_VERSION=2.1.3
-DOCKER_VERSION=1.13.1
-DOCKER_DISTRIB=.pkg/docker-$(DOCKER_VERSION).tgz
-DOCKER_DISTRIB_URL=https://get.docker.com/builds/Linux/x86_64/docker-$(DOCKER_VERSION).tgz
 RUNSVINIT=vendor/runsvinit/runsvinit
 CODECGEN_DIR=vendor/github.com/ugorji/go/codec/codecgen
 CODECGEN_EXE=$(CODECGEN_DIR)/bin/codecgen_$(shell go env GOHOSTOS)_$(shell go env GOHOSTARCH)
@@ -47,9 +44,6 @@ IMAGE_TAG=$(shell ./tools/image-tag)
 
 all: $(SCOPE_EXPORT)
 
-$(DOCKER_DISTRIB):
-	curl -o $(DOCKER_DISTRIB) $(DOCKER_DISTRIB_URL)
-
 docker/weave:
 	curl -L https://github.com/weaveworks/weave/releases/download/v$(WEAVENET_VERSION)/weave -o docker/weave
 	chmod u+x docker/weave
@@ -61,15 +55,12 @@ docker/weaveutil:
 docker/%: %
 	cp $* docker/
 
-docker/docker: $(DOCKER_DISTRIB)
-	tar -xvzf $(DOCKER_DISTRIB) docker/docker
-
 %.tar: docker/Dockerfile.%
 	$(SUDO) docker build -t $(DOCKERHUB_USER)/$* -f $< docker/
 	$(SUDO) docker tag $(DOCKERHUB_USER)/$* $(DOCKERHUB_USER)/$*:$(IMAGE_TAG)
 	$(SUDO) docker save $(DOCKERHUB_USER)/$*:latest > $@
 
-$(CLOUD_AGENT_EXPORT): docker/Dockerfile.cloud-agent docker/$(SCOPE_EXE) docker/docker docker/weave docker/weaveutil
+$(CLOUD_AGENT_EXPORT): docker/Dockerfile.cloud-agent docker/$(SCOPE_EXE) docker/weave docker/weaveutil
 
 $(SCOPE_EXPORT): docker/Dockerfile.scope $(CLOUD_AGENT_EXPORT) docker/$(RUNSVINIT) docker/demo.json docker/run-app docker/run-probe docker/entrypoint.sh
 

docker/Dockerfile.cloud-agent

@@ -4,7 +4,6 @@ LABEL works.weave.role=system
 WORKDIR /home/weave
 RUN apk add --update bash conntrack-tools iproute2 util-linux curl && \
 	rm -rf /var/cache/apk/*
-ADD ./docker /usr/local/bin/
 ADD ./weave ./weaveutil /usr/bin/
 COPY ./scope /home/weave/
 ENTRYPOINT ["/home/weave/scope", "--mode=probe", "--no-app", "--probe.docker=true"]