Prefer container name to linked name

Summary:
A Docker container has several name:

• the container name
• a set of <base container>/<link name> when the container is linked to

Even if --link is deprecated, it's still valuable to implement a quick check
to select a name without slash if available.

Test Plan:
Test on Dwellers:

• before: RabbitMQ containers had nasqueron/mq as name
• after: white-rabbit is well the name printed

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1835