Fix example about ps and linked containers
Fix example about ps and linked containers

Signed-off-by: Alexander Morozov <4efb7da3e38416208b41d8021a942884d8a9435c@docker.com>

AdamOssenford/docker-pi,josemonsalve2/docker,ClusterHQ/docker-plugins,seanmcdaniel/docker,carlye566/docker_eric,carlye566/docker_eric,josemonsalve2/docker,ClusterHQ/docker-plugins,carlye566/docker_eric,josemonsalve2/docker,ClusterHQ/docker-plugins,seanmcdaniel/docker,seanmcdaniel/docker,AdamOssenford/docker-pi,AdamOssenford/docker-pi