API v1.41 adds a new option to get the number of desired
and running tasks when listing services. This patch enables
this functionality, and provides a fallback mechanism when
the ServiceStatus is not available, which would be when
using an older API version.
Now that the swarm.Service struct captures this information,
the `ListInfo` type is no longer needed, so it is removed,
and the related list- and formatting functions have been
modified accordingly.
To reduce repetition, sorting the services has been moved
to the formatter. This is a slight change in behavior, but
all calls to the formatter performed this sort first, so
the change will not lead to user-facing changes.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>