Switch artifact tests from ssh to syslog-ng logs transport

[dimakr]

Syslog-ng setup is now working good enough for local development as well as for cloud environments, so we can plan and implement switching from ssh to syslog-ng logs transport there.

[roydahan]

If it's only to remove the "logs_transport: 'ssh' " from yaml and it works, let's just do it.
If it gets complicated more than that, let's leave it as is.