ACCUMULO-1110 avoid locking the tablet to get file counts

git-svn-id: https://svn.apache.org/repos/asf/accumulo/branches/1.5@1451339 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-1110 avoid locking the tablet to get file counts

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1451340 13f79535-47bb-0310-9956-ffa450edef68