sys-apps/systemd: Add AWS and Azure network defaults

Adds zz-aws-default.network and zz-azure-default.network files to be
used as fallbacks on AWS and Azure, respectively. These files are only
included in the image on boards built for those platforms. Currently,
they only differ from zz-default.network because they enable IPv6 by
default. Changing zz-default.network to enable IPv6 by default in other
boards is more risky and requires more testing.

BUG=b/335451071
TEST=presubmit; enable IPv6 on arion instance in GCP and verify that IPv6 address is mapped to eth0 when fallback network file is used; enable IPv6 on lakitu instance in GCP and verify that IPv6 address is NOT mapped to eth0 when fallback network file is used (current behavior)
RELEASE_NOTE=Add IPv6 support for endor boards.

Change-Id: I2367bf96db46ab131f94833a292971f9d2f7a7dd
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/71050
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
4 files changed