`container_link_and_run_command` starts a new container which is
linked to another container with the link alias $APP_NAME and
execute a command in the newly created container.
VOLUMES is set to `$VOL_PREFIX/data:$VOL_PREFIX/conf:$VOL_PREFIX/logs`
by default. But some images may expose different paths. For example,
the tomcat image exposes `/app` and `$VOL_PREFIX/conf` and
`$VOL_PREFIX/logs` paths as volumes. The VOLUME variable allows us to
override the default volume paths with ones exposed by the image being
tested.
