ACCUMULO-3280 Clean up Initialize

  Stop creating unneeded metadata table dirs on every volume.
  Limit the impact of warnings suppression when using deprecated items.
  Remove redundant call to configure metadata tables in ZooKeeper.
  Improve log message for fs.defaultFS being file:///
  Remove redundant check for directory existance when creating some dirs.
  Ensure root tablet dir is UTF-8 encoded in ZooKeeper.
  Simplify methods to write out initial root tablet content.
Merge branch '1.6'

Conflicts:
	server/base/src/main/java/org/apache/accumulo/server/ServerConstants.java
	server/base/src/main/java/org/apache/accumulo/server/init/Initialize.java
Merge remote-tracking branch 'origin/master'