Automatic merge from submit-queue (batch tested with PRs 38760, 38213)

Avoid exporting fluentd-gcp own logs

To prevent fluentd from exporting its own logs, redirect the output to a file. Ability to read fluentd logs remains, but because these logs will not be exported, we can increase the verbosity of these logs.

Same change should be made for fluentd-es image.

CC @piosz