update vendoring dependencies

vendor/github.com/docker/distribution/Dockerfile

@@ -1,19 +1,18 @@
-FROM golang:1.4
-
-RUN apt-get update && \
-    apt-get install -y librados-dev apache2-utils && \
-    rm -rf /var/lib/apt/lists/*
+FROM golang:1.6-alpine
 
 ENV DISTRIBUTION_DIR /go/src/github.com/docker/distribution
-ENV GOPATH $DISTRIBUTION_DIR/Godeps/_workspace:$GOPATH
-ENV DOCKER_BUILDTAGS include_rados include_oss include_gcs
+ENV DOCKER_BUILDTAGS include_oss include_gcs
 
 WORKDIR $DISTRIBUTION_DIR
 COPY . $DISTRIBUTION_DIR
 COPY cmd/registry/config-dev.yml /etc/docker/registry/config.yml
+
+RUN set -ex \
+    && apk add --no-cache make git
+
 RUN make PREFIX=/go clean binaries
 
 VOLUME ["/var/lib/registry"]
 EXPOSE 5000
 ENTRYPOINT ["registry"]
-CMD ["/etc/docker/registry/config.yml"]
+CMD ["serve", "/etc/docker/registry/config.yml"]