* Fix bug: too many cloudwatch metrics
Cloudwatch metrics were being added incorrectly. The most obvious
symptom of this was that too many metrics were being added. A simple
check against the name of the metric proved to be a sufficient fix. In
order to test the fix, a metric selection function was factored out.
* Go fmt cloudwatch
* Cloudwatch isSelected checks metric name
* Move cloudwatch line in changelog to 1.2 features
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