While the class docker::services already allowed arrays to be
specified for `publish` ports, it didn't handle this correctly since
this array was simply converted to a string and passed onto Docker,
like so:

    --publish '["80:80", "443:443"]'

To correctly publish multiple ports, the `--publish` parameter has to
be called specified for each port.

    --publish '80:80' --publish '443:443'

This patch also introduces a new spec test to check this behavior

Allows attaching the service to one or multiple networks

The module previously allowed specifying the command parameter to
docker::services as an array, but did not correctly parse it as
such (output with square brackets and quotations marks to docker).
This patch fixes this behavior.