Mark docker-manifest command as experimental (cli)
Mark docker-manifest command as experimental (cli)

Signed-off-by: Vincent Demeester <87e1f221a672a14a323e57bb65eaea19d3ed3804@sbr.pm>

dnephin/cli,docker/cli,dnephin/cli,docker/cli,thaJeztah/cli,cpuguy83/cli,thaJeztah/cli,cpuguy83/cli