Coverity: Handle '"upload_permitted":false' as a warning, not an error

Using matrix of builds can give errors because when a job uploaded
analysis results, the curl command status (line 43) change from
'{"upload_permitted":true}' to
{"upload_permitted":false,"next_upload_permitted_at":"<date>"}

For some jobs of the same build, the status can be set to failed (exit 1),
so the build status is failed, same for the project.

To avoid this, it would be useful to handle '"upload_permitted":false' as a
warning, changing 'exit 1' to 'exit 0'.

The results of Coverity analysis is given via Coverity postprocessing.