[PYTHON] Handling of absolute paths of os.path.join

Note that if the argument has an absolute path, the argument before it will be ignored.

(ref. https://docs.python.org/3.3/library/os.path.html#os.path.join)

`python:os.path.join`


>>> os.path.join('/test', '/hoge', '/piyo')
'/piyo'

>>> os.path.join('/test', 'hoge', '/piyo')
'/piyo'

>>> os.path.join('/test', 'hoge', 'piyo')
'/test/hoge/piyo'