In Elasticsearch 5.0.0, by default unquoted field names in JSON will be
rejected. This can cause issues, however, for documents that were
already indexed with unquoted field names. To alleviate this, a system
property has been added that can be enabled so migration can occur.
This system property will be removed in Elasticsearch 6.0.0
Resolves#17674
The available memory metric was always set to `0` since 2.0.beta1 (bug). was left behind but never set. Turns out the section wasn't that useful, as it would only output the total memory available throughout all nodes in the cluster. We decided to remove the section then.