Bump fluentd image from 1.6.37 to 1.9.3.
Bump fluentd image from 1.6.37 to 1.9.3.

The primary reason is to include the fix for
https://github.com/GoogleCloudPlatform/fluent-plugin-google-cloud/issues/393,
which seems to be affecting us.

I have tried to compare throughput performance between the two versions,
using a single fixed spammy pod (logging many MB/s).
I am not seeing any significant difference in throughput or CPU usage.

b/205263713

Change-Id: I5263e03d7785b0890804310f9788347ab392a7ab
GitOrigin-RevId: 45856c3eeb056e743af52dd0cec1041a36c04cac

googlecloudrobotics/core,googlecloudrobotics/core,googlecloudrobotics/core