Add ecs-serviceconnect to CNI and Agent build scripts

[yinyic]

Summary

Add ecs-serviceconnect to CNI and Agent build scripts invoked by make target dockerfree-agent-image.

We are seeing below error when running SC:

error="add network failed: failed to find plugin \"ecs-serviceconnect\" in path [/amazon-ecs-cni-plugins]"

Implementation details

Testing

New tests cover the changes: no

% sudo make dockerfree-agent-image
...
Built ecs-serviceconnect plugin.
...
+ cp ./misc/plugins/ecs-serviceconnect rootfs/amazon-ecs-cni-plugins/ecs-serviceconnect
...

Using the generated ECS Agent image, I replaced the ECS Agent on an existing ECS Optimized AMI;

Before replacing, ecs-serviceconnect binary is missing

$ docker ps
CONTAINER ID   IMAGE                            COMMAND    CREATED          STATUS                    PORTS     NAMES
5f4144ccd269   amazon/amazon-ecs-agent:latest   "/agent"   47 minutes ago   Up 47 minutes (healthy)             ecs-agent
[ec2-user@ip-172-31-3-30 ~]$ docker export 5f4144ccd269 | tar -tf - | grep plugins
amazon-ecs-cni-plugins/
amazon-ecs-cni-plugins/aws-appmesh
amazon-ecs-cni-plugins/ecs-bridge
amazon-ecs-cni-plugins/ecs-eni
amazon-ecs-cni-plugins/ecs-ipam
amazon-ecs-cni-plugins/vpc-branch-eni
etc/docker/plugins/
run/docker/plugins/

After replacing, ecs-serviceconnect is now present

$ docker ps
CONTAINER ID   IMAGE                            COMMAND    CREATED         STATUS                            PORTS     NAMES
4fd68939ffba   amazon/amazon-ecs-agent:latest   "/agent"   3 seconds ago   Up 2 seconds (health: starting)             ecs-agent
[ec2-user@ip-172-31-3-30 ~]$ docker export 4fd68939ffba | tar -tf - | grep plugins
amazon-ecs-cni-plugins/
amazon-ecs-cni-plugins/aws-appmesh
amazon-ecs-cni-plugins/ecs-bridge
amazon-ecs-cni-plugins/ecs-eni
amazon-ecs-cni-plugins/ecs-ipam
amazon-ecs-cni-plugins/ecs-serviceconnect
amazon-ecs-cni-plugins/vpc-branch-eni
etc/docker/plugins/
run/docker/plugins/

Description for the changelog

Add ecs-serviceconnect to CNI and Agent build scripts

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[Realmonia]

Can you change target to aws:dev?