Change event source of TSI to IoTHub

[zhang-hua]

Description and Motivation

...

Change type

• [x] Bug fix
• [ ] New feature
• [ ] Enhancement
• [ ] Breaking change (breaks backward compatibility)

Checklist:

• [x] All tests passed
• [ ] The code follows the code style and conventions of this project
• [ ] The change requires a change to the documentation
• [ ] I have updated the documentation accordingly

---

This change is 

[molly-moen]

why is this change needed? what was the issue?

[zhang-hua]

@molly-moen this change is trying to fix the issue of no data showing up in TSI caused by the event source connection. This is suggested by TSI team.