[refactor] improve code readability by reducing if-statement levels

Change-Id: I846a74e3525b0de986b95a05e8a39b476c3daa91
Reviewed-on: http://gerrit.cloudera.org:8080/19239
Tested-by: Kudu Jenkins
Reviewed-by: Yuqi Du <shenxingwuying@gmail.com>
Reviewed-by: Yifan Zhang <chinazhangyifan@163.com>
Reviewed-by: Alexey Serbin <alexey@apache.org>
1 file changed