The shadow of board does not always show

[jingyanjingyan]

Describe the bug
The shadow of board does not always show

To Reproduce
Steps to reproduce the behavior:

1. jobs = %adl listjobs --account devtooltelemetryadla --page_index 0 --page_job_number 100000
2. Move the vertical and horizontal scroll bar

Expected behavior
The shadow of board should always show.

Screenshots
When move the vertical and horizontal scroll bar, the shadow of board does not show sometimes.

Desktop (please complete the following information):
OS: Win10
Browser: chrome
Jupyter Version: Python 3.6.2, Jupyter 4.4.0

Additional context
Add any other context about the problem here.

[gaoyangxiaozhu]

This looks like a error or problem occurred at the UI layer of jupyter notebook. As we haven't started to do ui-level functionality improvement and customization (we still use the native UI provided by jupyter) yet, so all of these issues will be left unaddressed for now. @ruixinxu @jingyanjingyan