We have 'quiet' mode where only minimal data is printed to the console.
But there were no logs at all then.
This change generates log files (if 'logs-dir' argument is used) during
quiet build.
Also enables 'quiet' mode for CI so Zuul will not have to parse 29MB
JSON file each time.
Change-Id: If7d5c2807f0947a8bbbc1ceb8531c9b9c9287c1f
0cf5b1d4e6