control: add missing fields

Without section/priority, reprepro will reject the packages. Add
sections following the Debian docker.io packages

Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

hack/make/.build-deb/control

@@ -1,5 +1,8 @@
 Source: docker-engine
+Section: admin
+Priority: optional
 Maintainer: Docker <support@docker.com>
+Standards-Version: 3.9.6
 Homepage: https://dockerproject.org
 Vcs-Browser: https://github.com/docker/docker
 Vcs-Git: git://github.com/docker/docker.git