Update error prefix of v4 container stats endpoint for task lookup failure case

[amogh09]

Summary

There is a discrepancy in the prefix of error message returned by v4 container stats endpoint between task lookup failure and container lookup failure cases.

Task lookup failure

"V4 container handler: unable to get task arn from request:  unable to get task Arn from v3 endpoint ID: <v3EndpointID>"

vs

Container lookup failure

"V4 container stats handler: unable to get container ID from request: unable to get docker ID from v3 endpoint ID: <v3EndpointID>"

That is, V4 container handler vs V4 container stats handler. We consider the former a bug and this PR makes the prefix for the two cases consistent by converging to V4 container stats handler. This discrepancy does not exist in V3 container stats endpoint and it uses V3 container stats handler prefix for both cases.

Note that there are some unrelated changes in this PR which are a result of running go mod vendor for agent module. The vendor directory for agent module is out of sync.

Implementation details

• Add error prefix strings to TMDS handlers package in ecs-agent module.
• Update container stats and task stats handlers in ecs-agent module to use the error prefix when generating error response for lookup failure cases.
• Remove error prefixes from errors returned by the implementation of GetContainerStats and GetTaskStats methods in agent module.

Testing

Built Agent from source, installed it on an EC2 instance, and invoked v4 container stats endpoint with a bad endpoint container ID.

Before

$ curl -s http://169.254.170.2/v4/bad/stats | jq
"V4 container handler: unable to get task arn from request: unable to get task Arn from v3 endpoint ID: bad"

After

$ curl -s http://169.254.170.2/v4/bad/stats | jq
"V4 container stats handler: unable to get task arn from request: unable to get task Arn from v3 endpoint ID: bad"

New tests cover the changes: yes

Description for the changelog

Update error prefix of v4 container stats endpoint for task lookup failure case

Licensing

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

[xxx0624]

LGMT. Thank you for taking care of this!