Implement logging.getChild() with join() (not in 2.6) in other places

the patch is like 685a57ed762a9a6e7aea420a6189c3651b03f018

Signed-off-by: Rongze Zhu <zrzhit@gmail.com>
Merge pull request #145 from zhurongze/fix-getChild-AttributeError-in-other-places

Implement logging.getChild() with join() (not in 2.6) in other places