travis-ci: sonar-scanner: stop producing debug output
travis-ci: sonar-scanner: stop producing debug output

Results in huge build logs, which results in travis killing the job.

LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed