app-admin/stackdriver: rename container log fields

This change modifies the cos specific fluentd config used
by the logging agent so that metadata field keys names
(such as 'stream' and 'container_id') are unique to avoid
potential collisions with user created key names within
json logs. Also adds some clarification comments.

See b/137508822#comment24 for examples of new behavior.

Comment on release note being None: this change
preemptively fixes an issue that was introduced with CL
10520, therefore another release note would be redundant.

BUG=b/137508822
TEST=presubmit, validated behavior on VM
RELEASE_NOTE=None

Change-Id: I21d5aea85dfc2deed071d72909815aa8de49a9ed
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/10700
Reviewed-by: Roy Yang <royyang@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
2 files changed