ACCUMULO-1481 create the root table entry in zookeeper, but blocked by ACCUMULO-1814
ACCUMULO-1637 Update the HDFS configuration check in VolumnManagerImpl
from the one in TabletServer.

Looks like I missed the movement of the configuration validation code in
1.6.0 from TabletServer to VolumeManagerImpl. Updated the check, and
fixed the unit test to invoke the correct code.