The original Compose config loading used the `compose` tag, which
was replaced by mapstructure. Some fields were left on the old tag. This
commit removes the old tag and uses types and mapstructure.
Signed-off-by: Daniel Nephin <dnephin@docker.com>
Upstream-commit: daaeeafa7ae3a4afbff530861a9ed4a97e2c431f
Component: engine