This commit clarifies the autoscaling feature flag registration system
property. The intention is that this system property is:
- unset in snapshot builds
- unset, true, or false in release builds
- in release builds, unset behaves the same as false
- therefore, we only register the enabled flag if the build is a
snapshot build, or the build is a release build and the system
property is set to true
This commit clarifies that intention, and removed a confusion situation
where the AUTOSCALING_FEATURE_FLAG_REGISTERED field would be set to
false in a snapshot build, even though we were going to register the
setting.