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)

Docker-DCO-1.1-Signed-off-by: Tianon Gravi <admwiggin@gmail.com> (github: crosbymichael)
Upstream-commit: 75293b12b36b3eef6706cf85f291be96500a40da
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 \