Automatic merge from submit-queue (batch tested with PRs 38592, 39949, 39946, 39882)

Remove fluentd buffers if fluentd is stuck

Fluentd now stores its buffers on disk for the resiliency. However, if buffer is corrupted, fluentd will be restarting forever.

Following change will make fluentd liveness probe delete buffers if fluentd is stuck for more than X minutes (15 by default).