Since it rus on every (human) comment, the release-approval pipeline
can get pretty noisy. It's also not that critical to read (failure
generally meaning that you don't have the required +1s yet).
This change disables comment posting on success/failure in the pipeline.
Change-Id: I4808a84cd39a5a19ddad86b548ec18d8cadf7430
d11e9ce9aa