HDFS block caches are not dynamically resized on configuration change.

I noticed that the graph for Data Block Cache was constantly at zero, despite me changing the configuration and ensuring that it was enabled for the metadata table. Upon looking at the configuration, I saw that I configured it to 256 (bytes) instead of 256MB. After using the Accumulo shell to change the configuration, the cache was not immediately used. After I restarted the tservers, then the cache was used.

We should try to find a way to dynamically resize the caches on the fly to avoid the need of restarting all tabletservers.