RMAppState isn't a public facing enum like YarnApplicationState, so we shouldn't return values or list filters that come from it. However, some Blocks and AppInfo are still using RMAppState.
It is not 100% clear to me whether or not fixing this would be a backwards-incompatible change. The change would only reduce the set of possible strings that the API returns, so I think not. We have also been changing the contents of RMAppState since 2.2.0, e.g. in
YARN-891. It would still be good to fix this ASAP (i.e. for 2.2.1).