Add support for 15.04, add systemd note for 15.04
Add support for 15.04, add systemd note for 15.04

Fixes #12002

Signed-off-by: Ankush Agarwal <fbce221e53f28a6368ebb5e0aa2ee1c79ff12e9e@gmail.com>

ewindisch/docker,ewindisch/docker,ewindisch/docker