#### Why I did it
To incorporate the below changes in DellEMC S5232, Z9264, Z9332 platforms.
- Update thermal high threshold values
- Make watchdog API Python2 and Python3 compatible
- Fix LGTM alerts
- Z9264: Fix get_change_event timer value
#### How I did it
- Use 'universal_newlines=True' in subprocess.Popen call.
- Change the timeout in 'get_change_event' to milliseconds to match specification in sonic_platform_common/chassis_base.py
142d93b80a