Distributed Grain Directory followup work

[ReubenBond]

There are some things we need to do before taking the experimental attribute off the new grain directory and eventually making it the default.

1. Implement a relatively smooth rolling upgrade strategy from the old directory to the new one. One idea is to implement the old grain directory system target interfaces in the new grain directory.
2. Reduce log noise. Most info and even warning level logs can be made debug logs.
3. Enable the directory everywhere, even with no grains using it.