Fix chunkserver Block::Append()
Fix chunkserver Block::Append()

00k/ToyDFS,yvxiang/coverage_for_bfs,myawan/bfs-1,yvxiang/dfs,myawan/bfs-1,lylei/dfs,bluebore/dfs,yvxiang/coverage_for_bfs,linyvxiang/dfs,lylei/dfs,lylei/dfs,00k/ToyDFS,yvxiang/dfs,myawan/bfs-1,imotai/bfs,bluebore/bfs,baidu/bfs,bluebore/dfs,baidu/bfs,imotai/bfs,linyvxiang/dfs,yvxiang/dfs,lylei/dfs,imotai/bfs,baidu/bfs,linyvxiang/dfs,bluebore/bfs,baidu/bfs,myawan/bfs-1,yvxiang/coverage_for_bfs,yvxiang/dfs,bluebore/bfs,bluebore/dfs,yvxiang/coverage_for_bfs