Test and document updating app config.

The following is feedback from @joshelser on this [mailing list thread](https://lists.apache.org/thread.html/f4fabfec7ce8c70f599691b249f0ef96a36c021e3c0e83c9f350d4cd@%3Cdev.fluo.apache.org%3E) and my response. Need to test and document updating app config.

> > - Application Configuration
> >
> > Nit: s/zookeeper/ZooKeeper/ (really, Apache ZooKeeper would be better)
> > s/fluo/Fluo/
> >
> > "After fluo is initialized this information can be accessed anywhere by
> > calling.." -- Technical question: is this always pulling a fresh copy from
> > ZK? Or, maybe subject to the same Watcher-fire config propagation issue that
> > Accumulo is?
>
> Thats a really good question and I am not sure what the answer is. I
> have not tried doing this. I have only set app config at
> nitialization time before starting the application. I will open an
> issue about testing this and documenting expected behavior.

The issue names no files or tests; start with the linked mailing-list thread and the application-configuration behavior described there. Verify what happens when app configuration changes after initialization, then add coverage for the observed behavior and document the expected result.

Written by the indexing model from the issue text.