[Mellanox] Fix chassis test issue

[stephenxs]

Fix compiling issue

=================================== FAILURES =================================== 
____________________ TestChassis.test_get_port_or_cage_type ____________________ 
self = <tests.test_chassis.TestChassis object at 0x7f7e81fecaf0> 
def test_get_port_or_cage_type(self): 
chassis = Chassis() 
> chassis.RJ45_port_list = [0] 
E AttributeError: can't set attribute 
tests/test_chassis.py:289: AttributeError 
=============================== warnings summary ============

It was caused by #11336 but the root cause is that the ci/merge flow of PR #11336 and #11436 interleaved.

Signed-off-by: Stephen Sun stephens@nvidia.com

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• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205

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Link to config_db schema for YANG module changes

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