ACCUMULO-1478 prevent NPE when starting the shell

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1490335 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-1486 handle absence of sync method

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1490379 13f79535-47bb-0310-9956-ffa450edef68