[Bug]: [drop_packets/drop_packets.py][DNX] 'RX_DRP' drop counter was not incremented on Port Channels

[kenneth-arista]

Issue Description

Tracking failures seen in drop_packets/drop_packets.py on T2 and T2-min

Results you see

Failed: 'RX_DRP' drop counter was not incremented on iface Ethernet40. DUT RX_DRP == [0, 0]; Sent == 1000

Results you expected to see

The test should pass

Is it platform specific

broadcom

Relevant log output

def _check_drops_on_dut():
            return packets_count in _get_drops_across_all_duthosts()

        if not wait_until(25, 1, 0, _check_drops_on_dut):
            # We were seeing a few more drop counters than expected, so we are allowing a small margin of error
            # The max number of unexpected drop we see equals to the number of vlan members in t0 topology
            duthost = duthosts.frontend_nodes[0]
            mg_facts = duthost.minigraph_facts(host=duthost.hostname)["ansible_facts"]
            DROP_MARGIN = 0 if mg_facts['minigraph_vlans'] else 10
            for vlan in mg_facts['minigraph_vlans']:
                DROP_MARGIN += len(mg_facts['minigraph_vlans'][vlan]['members'])
            logger.info(f"The DROP_MARGIN is {DROP_MARGIN}")
            actual_drop = _get_drops_across_all_duthosts()
            for drop in actual_drop:
                if drop >= packets_count and drop <= packets_count + DROP_MARGIN:
                    logger.warning("Actual drops {} exceeded expected drops {} on iface {}\n".format(
                        actual_drop, packets_count, dut_iface))
                    break
            else:
                fail_msg = "'{}' drop counter was not incremented on iface {}. DUT {} == {}; Sent == {}".format(
                    column_key, dut_iface, column_key, actual_drop, packets_count)
>               pytest.fail(fail_msg)
E               Failed: 'RX_DRP' drop counter was not incremented on iface Ethernet40. DUT RX_DRP == [0, 0]; Sent == 1000

DROP_MARGIN = 10
_check_drops_on_dut = <function verify_drop_counters.<locals>._check_drops_on_dut at 0x7f55d4d10280>
_get_drops_across_all_duthosts = <function verify_drop_counters.<locals>._get_drops_across_all_duthosts at 0x7f55d4d109d0>
actual_drop = [0, 0]
asic_index = None
column_key = 'RX_DRP'
drop       = 0
dut_iface  = 'Ethernet40'
duthost    = <MultiAsicSonicHost nfc420-7>
duthosts   = [<MultiAsicSonicHost nfc420-7>, <MultiAsicSonicHost nfc420-8>, <MultiAsicSonicHost nfc420>]
fail_msg   = "'RX_DRP' drop counter was not incremented on iface Ethernet40. DUT RX_DRP == [0, 0]; Sent == 1000"
get_cnt_cli_cmd = 'portstat -j '
mg_facts   = {'deployment_id': '1', 'dhcp_servers': [], 'dhcpv6_servers': [], 'forced_mgmt_routes': ['10.64.0.0/14', '10.80.0.0/12', '172.16.0.0/12', '10.224.0.0/11', '10.100.248.0/22', '10.100.252.0/22', ...], ...}
packets_count = 1000

common/helpers/drop_counters/drop_counters.py:134: Failed

### Output of `show version`

_No response_

### Attach files (if any)

_No response_

[kenneth-arista]

This problem is seen on only Port Channels on DNX platforms. We see the issue regardless if port-channel members are on the same or different cores.

Opened Broadcom CS case: CS00012379105

[kenneth-arista]

@arlakshm @vmittal-msft @ysmanman @arista-nwolfe for awareness

[kenneth-arista]

Potentially related to sonic-net/sonic-mgmt#15051 (corresponding Brcm case CS00012373986)