'src/contrib/zooinspector/NOTICE.txt' isn't complying to '.gitattributes' in branch-3.4

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/branches/branch-3.4@1604669 13f79535-47bb-0310-9956-ffa450edef68
ZOOKEEPER-1746. add docs and tests for AsyncCallback interfaces