[psud] psud keeps reporting WARNING

[bingwang-ms]

Description
psud keeps reporting WARNING in syslog on lattest image.

syslog.29.gz:Dec  3 14:49:59.614039 str2-dx010-acs-6 WARNING pmon#psud[32]: message repeated 33 times: [ Failed to update PSU data - float() argument must be a string or a number]
syslog.29.gz:Dec  3 14:50:01.340192 str2-dx010-acs-6 WARNING pmon#psud[32]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:50:03.953308 str2-dx010-acs-6 WARNING pmon#psud[32]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:50:04.500500 str2-dx010-acs-6 WARNING pmon#psud[32]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:50:40.485500 str2-dx010-acs-6 WARNING pmon#psud[32]: message repeated 21 times: [ Failed to update PSU data - float() argument must be a string or a number]
syslog.29.gz:Dec  3 14:51:13.593958 str2-dx010-acs-6 WARNING pmon#psud[31]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:51:15.883878 str2-dx010-acs-6 WARNING pmon#psud[31]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:51:16.856614 str2-dx010-acs-6 WARNING pmon#psud[31]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:51:18.432881 str2-dx010-acs-6 WARNING pmon#psud[31]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:51:20.029652 str2-dx010-acs-6 WARNING pmon#psud[31]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:52:09.755415 str2-dx010-acs-6 WARNING pmon#psud[31]: message repeated 29 times: [ Failed to update PSU data - float() argument must be a string or a number]
syslog.29.gz:Dec  3 14:52:10.921210 str2-dx010-acs-6 WARNING pmon#psud[31]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:53:09.805632 str2-dx010-acs-6 WARNING pmon#psud[31]: message repeated 35 times: [ Failed to update PSU data - float() argument must be a string or a number]
syslog.29.gz:Dec  3 14:53:09.806763 str2-dx010-acs-6 WARNING pmon#psud[31]: Failed to update PSU data - float() argument must be a string or a number
syslog.29.gz:Dec  3 14:53:10.630257 str2-dx010-acs-6 WARNING pmon#psud[31]: Failed to update PSU data - float() argument must be a string or a number

Steps to reproduce the issue:

1. Run nightly test, and the WARNING will be in syslog. Still not clear how triggered.

Describe the results you received:

Describe the results you expected:

Additional information you deem important (e.g. issue happens only occasionally):

**Output of `show version`:**

SONiC Software Version: SONiC.master.435-63c1afbc
Distribution: Debian 10.6
Kernel: 4.19.0-9-2-amd64
Build commit: 63c1afbc
Build date: Wed Oct  7 04:39:39 UTC 2020
Built by: johnar@jenkins-worker-8

Platform: x86_64-cel_seastone-r0
HwSKU: Celestica-DX010-C32
ASIC: broadcom
Serial Number: DX010F2B118711MS100005
Uptime: 03:40:28 up  3:12,  1 user,  load average: 4.21, 2.10, 2.08

Docker images:
REPOSITORY                    TAG                   IMAGE ID            SIZE
docker-teamd                  latest                3af522087f99        394MB
docker-teamd                  master.435-63c1afbc   3af522087f99        394MB
docker-sonic-mgmt-framework   latest                8c12c8be0438        486MB
docker-sonic-mgmt-framework   master.435-63c1afbc   8c12c8be0438        486MB
docker-router-advertiser      latest                069a18759d97        359MB
docker-router-advertiser      master.435-63c1afbc   069a18759d97        359MB
docker-platform-monitor       latest                79b56e8c2519        441MB
docker-platform-monitor       master.435-63c1afbc   79b56e8c2519        441MB
docker-lldp                   latest                6105a0f7ebac        388MB
docker-lldp                   master.435-63c1afbc   6105a0f7ebac        388MB
docker-dhcp-relay             latest                51f5ad814a06        366MB
docker-dhcp-relay             master.435-63c1afbc   51f5ad814a06        366MB
docker-database               latest                2841a8d13042        359MB
docker-database               master.435-63c1afbc   2841a8d13042        359MB
docker-orchagent              latest                5a2807cb3019        407MB
docker-orchagent              master.435-63c1afbc   5a2807cb3019        407MB
docker-nat                    latest                b18cd3797d95        396MB
docker-nat                    master.435-63c1afbc   b18cd3797d95        396MB
docker-sonic-telemetry        latest                06131575409c        429MB
docker-sonic-telemetry        master.435-63c1afbc   06131575409c        429MB
docker-fpm-frr                latest                f7cb016a76d1        410MB
docker-fpm-frr                master.435-63c1afbc   f7cb016a76d1        410MB
docker-sflow                  latest                622b50ca39c9        397MB
docker-sflow                  master.435-63c1afbc   622b50ca39c9        397MB
docker-snmp                   latest                24a9217c8ce2        399MB
docker-snmp                   master.435-63c1afbc   24a9217c8ce2        399MB
docker-syncd-brcm             latest                4efe9fd2f53e        542MB
docker-syncd-brcm             master.435-63c1afbc   4efe9fd2f53e        542MB

**Attach debug file `sudo generate_dump`:**

```
(paste your output here)
```