[TSC] TSC return 'Not consistent' in TSA(Maintenance) mode

[bingwang-ms]

Description
TSC return Not consistent state in TSA(Maintenance) mode, which should be System Mode: Maintenance.

admin@str-7260cx3-acs-2:~$ TSC
Traffic Shift Check:
System Mode: Not consistent

The rates are calculated within 5 seconds period
      IFACE    STATE    RX_OK      RX_BPS    RX_UTIL    RX_ERR    RX_DRP    RX_OVR    TX_OK      TX_BPS    TX_UTIL    TX_ERR    TX_DRP    TX_OVR
-----------  -------  -------  ----------  ---------  --------  --------  --------  -------  ----------  ---------  --------  --------  --------
  Ethernet0        U        0    0.00 B/s      0.00%         0         0         0        0    0.00 B/s      0.00%         0         0         0
  Ethernet2        U        0    0.00 B/s      0.00%         0         0         0        1   43.72 B/s      0.00%         0         0         0
  Ethernet4        U        0    0.00 B/s      0.00%         0         0         0        1   43.72 B/s      0.00%         0         0         0
......

Steps to reproduce the issue:

1. Run config reload to re-initialize DUT
2. Run TSA to enter Maintenance Mode

admin@str-7260cx3-acs-2:~$ TSA
System Mode: Normal -> Maintenance

3. Run TSC to check the current state of DUT, and will get System Mode: Not consistent, which I think should be System Mode: Maintenance.

The issue is observed on both 201911 and Master branch.

Describe the results you received:
TSC return 'Not consistent' in TSA(Maintenance) mode.

Describe the results you expected:
TSC should return System Mode: Maintenance in Maintenance mode.

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

**Output of `show version`:**

SONiC Software Version: SONiC.20191130.53
Distribution: Debian 9.13
Kernel: 4.9.0-11-2-amd64
Build commit: d7fee5665
Build date: Mon Nov 16 11:10:58 UTC 2020
Built by: sonicbld@jenkins-slave-phx-2

Platform: x86_64-arista_7260cx3_64
HwSKU: Arista-7260CX3-D108C8
ASIC: broadcom
Serial Number: SSJ17432414
Uptime: 08:48:14 up  7:14,  1 user,  load average: 1.06, 1.70, 1.91

Docker images:
REPOSITORY                 TAG                 IMAGE ID            SIZE
docker-snmp-sv2            20191130.53         ef2f0e7130d1        348MB
docker-snmp-sv2            latest              ef2f0e7130d1        348MB
docker-fpm-frr             20191130.53         eca656cbc4f6        335MB
docker-fpm-frr             latest              eca656cbc4f6        335MB
docker-acms                20191130.53         a14f1c36904a        199MB
docker-acms                latest              a14f1c36904a        199MB
docker-lldp-sv2            20191130.53         52e2a6835c62        312MB
docker-lldp-sv2            latest              52e2a6835c62        312MB
docker-orchagent           20191130.53         dd820682c3d0        333MB
docker-orchagent           latest              dd820682c3d0        333MB
docker-teamd               20191130.53         42f082f54287        315MB
docker-teamd               latest              42f082f54287        315MB
docker-syncd-brcm          20191130.53         8a0ab6fd0add        437MB
docker-syncd-brcm          latest              8a0ab6fd0add        437MB
docker-platform-monitor    20191130.53         d03937f77724        358MB
docker-platform-monitor    latest              d03937f77724        358MB
docker-sonic-telemetry     20191130.53         2f246407d224        353MB
docker-sonic-telemetry     latest              2f246407d224        353MB
docker-database            20191130.53         783b8cf466cb        289MB
docker-database            latest              783b8cf466cb        289MB
docker-router-advertiser   20191130.53         e2f364002783        289MB
docker-router-advertiser   latest              e2f364002783        289MB
docker-dhcp-relay          20191130.53         550c0169a836        299MB
docker-dhcp-relay          latest              550c0169a836        299MB
k8s.gcr.io/pause           3.2                 80d28bedfe5d        683kB

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

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