Update metrics interface to couple metric completion and publish

[amogh09]

Summary

Metrics Entry interface in ecs-agent module has a Done method that marks a metric as completed and returns a function that when called publishes the metric. It is supposed to be used like below.

  entry.Done(err)()

It is too easy to forget the trailing () which leads to metrics not being published. We don't really have a usecase to separate metrics completion and publish, so this PR updates the Done method's signature to not return a function. Instead, the method is suppose to do both - mark the metric as completed and publish it.

Implementation details

• Update Done method of Entry interface.
• Update usage and tests.

Testing

Automated tests only.

New tests cover the changes: no

Description for the changelog

Update metrics interface to couple metric completion and publish

Licensing

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