ACCUMULO-983 checkpointing exception handling improvements

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1437565 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-983 moved proxy tests into proxy package

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1437567 13f79535-47bb-0310-9956-ffa450edef68