getContainerByServiceName expects an instance name

#2314 brought support for selecting a container based on the service name when using docker-compose (thanks 🙌 !). However, the value it expects contains the "container number" (e.g. service_1), instead of just the service name, e.g. just service.

This does not match the behaviour of using docker-compose directly:

$ docker-compose ps agent
      Name             Command       State   Ports
--------------------------------------------------
myapp_agent_1   /bin/k3s agent   Up

$ docker-compose ps agent_1
ERROR: No such service: agent_1

According to this test, it looks like the expected behavior, or maybe was incorrectly modeled.

Maybe using getServiceInstanceName from getContainerByServiceName would provide compatibility for both cases?

Empieza leyendo getContainerByServiceName y el test al que se hace referencia en el pull request #2314; después, compara la búsqueda actual con el comportamiento de docker-compose ps service-name. Se considera terminado cuando la búsqueda acepta el nombre del servicio de forma coherente, conservando cualquier compatibilidad prevista con instance-name, y el test correspondiente se ha actualizado o añadido.