Fix IndexError in test_no_pfc

[bingwang-ms]

Description of PR

The PR is to fix IndexError in test case test_no_pfc.
The error is because the fixture lossless_prio_dscp_map always selects the first port in PORT_QOS_MAP table as the testing port, and selects the first profile in DSCP_TO_TC_MAP to get the DSCP to TC map. So on some particular topo, we saw the IndexError because the selected profile is not applied to the testing port.

>           traffic_params = {'dscp': dscp[0], 'dscp_bg': dscp_bg}
E           IndexError: list index out of range

This PR fixed the issue by checking the lossless priority and lossless_prio_dscp_map as well. The test case will be skipped if the extra lossless queue is not enabled on this port or the map lossless_prio_dscp_map for a particular priority is empty.

Summary:
Fixes IndexError in test case test_no_pfc.

Type of change

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

Back port request

• 201911
• 202012
• 202205
• 202305
• 202311

Approach

What is the motivation for this PR?

This PR is to address IndexError in test_no_pfc.

How did you do it?

This PR fixed the issue by checking the lossless priority and lossless_prio_dscp_map as well. The test case will be skipped if the extra lossless queue is not enabled on this port or the map lossless_prio_dscp_map for a particular priority is empty.

How did you verify/test it?

Verified on a dualtor testbed where I saw the new failure. Test can pass now.

collected 8 items                                                                                                                                                                                     

qos/test_pfc_pause.py::test_no_pfc[svcstr-7050-acs-3|2] SKIPPED (lossless prio 2 not enabled on testing port)                                                                                   [ 12%]
qos/test_pfc_pause.py::test_no_pfc[svcstr-7050-acs-3|3]  ^HPASSED                                                                                                                                  [ 25%]
qos/test_pfc_pause.py::test_no_pfc[svcstr-7050-acs-3|4] PASSED                                                                                                                                  [ 37%]
qos/test_pfc_pause.py::test_no_pfc[svcstr-7050-acs-3|6] SKIPPED (lossless prio 6 not enabled on testing port)                                                                                   [ 50%]
qos/test_pfc_pause.py::test_no_pfc[svcstr-7050-acs-4|2] SKIPPED (lossless prio 2 not enabled on testing port)                                                                                   [ 62%]
qos/test_pfc_pause.py::test_no_pfc[svcstr-7050-acs-4|3]  ^HPASSED                                                                                                                                  [ 75%]
qos/test_pfc_pause.py::test_no_pfc[svcstr-7050-acs-4|4] PASSED                                                                                                                                  [ 87%]
qos/test_pfc_pause.py::test_no_pfc[svcstr-7050-acs-4|6] SKIPPED (lossless prio 6 not enabled on testing port)                                                                                   [100%]

Any platform specific information?

No.

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

Not a new test case.

Documentation

[bingwang-ms]

MSFT ADO: 27317506

[bingwang-ms]

@StormLiangMS Please help approve the cherry-pick. Thanks!

[mssonicbld]

Cherry-pick PR to 202305: #12295

[mssonicbld]

Cherry-pick PR to 202311: #12296