Add ca-certificates to our package Recommends

It's only in "Recommends" because it's only required for all but the esoteric configurations (since you can't "docker pull" from the index without it, but that's about it).

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Upstream-commit: e5189b5dd2c044030e7e2ab7029eba0fe91c3b25
Component: engine

components/engine/hack/make/ubuntu

@@ -111,6 +111,7 @@ EOF
 		    --depends lxc \
 		    --depends aufs-tools \
 		    --depends iptables \
+		    --deb-recommends ca-certificates \
 		    --description "$PACKAGE_DESCRIPTION" \
 		    --maintainer "$PACKAGE_MAINTAINER" \
 		    --conflicts lxc-docker-virtual-package \