Support usage messages on bad flags.
Support usage messages on bad flags.

Signed-off-by: Daniel Nephin <6347c07ae509164cffebfb1e2a0d6ed64958db19@docker.com>

ashfall/cli,allencloud/cli,ashfall/cli,e11137/cli,redpanda/cli,redpanda/cli,cpuguy83/cli,gdevillele/cli,dnephin/cli,riyazdf/cli,docker/cli,docker/cli,e11137/cli,allencloud/cli,thaJeztah/cli,thaJeztah/cli,Zebrilee/cli,dnephin/cli,riyazdf/cli,Zebrilee/cli,cpuguy83/cli