docker::services: Fix using multiple published ports

[jacksgt]

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

[davejrt]

LGTM