range of data validation changed after setting data
*Created originally on Bitbucket by [kongyuan (Yuan Kong)](https://bitbucket.org/%7Be006e094-3b22-4324-a4e0-e6813fefc276%7D/)*
I created a small xlsx file with Excel 2013

yellow cells have data validation which refer to a list [1,2,3]
White cells have no validation
here is my code:
```
#!python
from openpyxl import load_workbook
workbook = load_workbook("test.xlsx")
worksheet = workbook.active
worksheet['A1'] = 1
workbook.save(filename="test.xlsx")
```
I expect A1 is set to 1, A3 is still blank, and A2 and A4 have no validation drop down.
But the actual is:

You can see A2 now have validation drop down, (which refer to a list [1,2,3])
I tried more and found all cells except last cell (A2, A3, A4, ... Ax-1) was set data validation.
*Attachments:* [test.xlsx](/uploads/e5d58832d8e0cb5b3f0bb310485ebbc7/test.xlsx)
issue