[202205 xfail] test_no_pfc xfail for 202205 branch

[XuChen-MSFT]

Description

This issue is to track test_no_pfc failure for 202205 branch

Steps to reproduce the issue: 1. 2. 3.

Describe the results you received:

Describe the results you expected:

Additional information you deem important:

**Output of `show version`:**

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

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

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

relevant failure message

        for dscp_bg in other_dscps:
            logger.info("Testing dscp: {} and background dscp: {}".format(dscp, dscp_bg))
            traffic_params = {'dscp': dscp[0], 'dscp_bg': dscp_bg}
            results = run_test(pfc_test_setup,
                               fanouthosts,
                               duthost,
                               ptfhost,
                               conn_graph_facts,
                               fanout_graph_facts,
                               traffic_params,
                               queue_paused=False,
                               send_pause=False,
                               pfc_pause=None,
                               pause_prio=None,
                               max_test_intfs_count=MAX_TEST_INTFS_COUNT)
    
            """ results should not be none """
            if results is None:
                test_errors += "Dscp: {}, Background Dscp: {}, Result is empty\n".format(dscp, dscp_bg)
    
            errors = dict()
            for intf in results:
                if len(results[intf]) != 2:
                    continue
    
                pass_count = results[intf][0]
                total_count = results[intf][1]
    
                if total_count == 0:
                    continue
    
                if pass_count < total_count * PTF_PASS_RATIO_THRESH:
                    errors[intf] = results[intf]
    
            if len(errors) > 0:
                test_errors += "Dscp: {}, Background Dscp: {}, errors occured: {}\n"\
                               .format(dscp, dscp_bg, " ".join(["{}:{}".format(k,v) for k, v in errors.items()]))
    
>       pytest_assert(len(test_errors) == 0, test_errors)
E       Failed: Dscp: [3], Background Dscp: 4, errors occured: Ethernet8:[0, 20] Ethernet12:[0, 20]
E       Dscp: [3], Background Dscp: 0, errors occured: Ethernet8:[0, 20] Ethernet12:[0, 20]
E       Dscp: [3], Background Dscp: 1, errors occured: Ethernet8:[0, 20] Ethernet12:[0, 20]

[ZhaohuiS]

@XuChen-MSFT Could you add the description and paste the error log here to make the community know what happened for this case? Thanks.

[XuChen-MSFT]

updated

[XuChen-MSFT]

E Dscp: [3], Background Dscp: 1, errors occured: Ethernet8:[0, 20] Ethernet12:[0, 20] As above, the symptom is, for some Ethernet port, no packet was received, even if already sent 20 packets. it's not generic issue for all platform, only for dualtor on 202205 branch.