Issue:

• The PSU FAN information is not updated in the redis-db.

Steps to reproduce

• Load latest master image and check redis-db PSU Fan table.

Logs:
root@sonic:~# redis-cli -n 6 hgetall "FAN_INFO|PSU1 Fan"
1) "led_status"
2) "None"

To fix this issue:

• Initialize self.presence and other variables in PsuStatus dunder init to False instead of True.
• Import datetime module.
• Then, the following values will be seen.

root@sonic:/# redis-cli -n 6 hgetall "FAN_INFO|PSU1 Fan"
1) "presence"
2) "True"
3) "status"
4) "Updating"
5) "direction"
6) "exhaust"
7) "speed"
8) "67"
9) "timestamp"
10) "20201223 01:48:55"
11) "led_status"
12) "None"

The one more issue is that since the PSU fan status values are "Updating/ N/A".
In system health daemon, the expected values for PSU fan status is "True/False".

• https://github.com/Azure/sonic-buildimage/blob/e88c7d11cae12a4973eca4f1ca9f4b4ba9facd71/src/system-health/health_checker/hardware_checker.py#L92

Thermalctld also updates the PSU Fan status value to "True/False".
So, need your input on whether we can change the PSU Fan status in psu daemon to return "True/False" instead of "Updating/ N/A".
If it is not done, then "PSU Fan is broken" error will be logged in redis-db for system health table.