[chassis] [arista] thermal info mismatch between platform.json and platform_api_conn

[wenyiz2021]

Description

(Pdb) expected_num_thermals
5
(Pdb) chassis.get_all_thermals(platform_api_conn)
[{u'__module__': u'arista.utils.sonic_platform.thermal', u'__class__': u'Thermal', u'object_id': u'0x7f5d70e8cfd0'}, {u'__module__': u'arista.utils.sonic_platform.thermal', u'__class__': u'Thermal', u'object_id': u'0x7f5d70e8e070'}, {u'__module__': u'arista.utils.sonic_platform.thermal', u'__class__': u'Thermal', u'object_id': u'0x7f5d70e8e0d0'}, {u'__module__': u'arista.utils.sonic_platform.thermal', u'__class__': u'Thermal', u'object_id': u'0x7f5d70e8e130'}, {u'__module__': u'arista.utils.sonic_platform.thermal', u'__class__': u'Thermal', u'object_id': u'0x7f5d70e8e190'}, {u'__module__': u'arista.utils.sonic_platform.thermal', u'__class__': u'Thermal', u'object_id': u'0x7f5d70e8e1f0'}]
(Pdb) len(chassis.get_all_thermals(platform_api_conn))
6
(Pdb) duthost.facts.get("chassis").get('thermals')
[{u'name': u'Cpu temp sensor'}, {u'name': u'Center back'}, {u'name': u'Fap0 core0'}, {u'name': u'Fap0 core1'}, {u'name': u'PCIE'}]

FAILED platform_tests/api/test_chassis.py::TestChassisApi::test_thermals[str2-7804-lc6-1] - Failed: Number of thermals (6) does not match expected number (5) FAILED platform_tests/api/test_chassis.py::TestChassisApi::test_thermals[str2-7804-lc7-1] - Failed: Number of thermals (6) does not match expected number (5)

Steps to reproduce the issue:

1. run test_chassis.py::test_thermals on arista chassis

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