Avoid erasing line for non-progress messages

The JSONMessage.Display methods erases the entire line by outputting the <ESC>[2K\r sequence before displaying the message content. This is not necessary for messages other than progress indicators, and introduces unwanted characters in the /events output.

Fixes #6203.

Docker-DCO-1.1-Signed-off-by: Arnaud Porterie <icecrime@gmail.com> (github: icecrime)
Merge pull request #6490 from icecrime/6203-artifacts_on_events_output

Avoid erasing line for non-progress messages