[Mellanox] Update test_exceeding_headroom due to adding checker when enabling SHP

[JibinBao]

Description of PR

Previously, when enabling SHP there is no checker even if the accumulative headroom(shared headroom) of a port exceeds the maximum threshold. Currently, we have added the checker for mellanox device, so we update the existing case test_exceeding_headroom to cover the scenarios enabling SHP.

The relevant PR: https://github.com/sonic-net/sonic-swss/pull/3272

Summary: Fixes # (issue)

Type of change

• [x] Bug fix
• [ ] Testbed and Framework(new/improvement)
• [ ] Test case(new/improvement)

Back port request

• [ ] 202012
• [ ] 202205
• [ ] 202305
• [ ] 202311
• [x] 202405

Approach

What is the motivation for this PR?

Add new case to cover new scenarios enabling SHP

How did you do it?

Update test_exceeding_headroom

How did you verify/test it?

Run test_exceeding_headroom on Mellanox device

Any platform specific information?

Mellanox

Supported testbed topology if it's a new test case?

Any

Documentation