Remove unnecessary fdb flush for test_configurable_drop_counters

[ZhaohuiS]

Signed-off-by: Zhaohui Sun zhaohuisun@microsoft.com

Description of PR

Summary:
Fixes # (issue)

Type of change

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

Back port request

• 201911
• 202012

Approach

What is the motivation for this PR?

test_configurable_drop_counters may cause orchagent crash during unshutdown interface/flush fdb/remove static fdb these operations.
Issue reported here: sonic-net/sonic-buildimage#11046

How did you do it?

The issue is fixed, but we can remove unnecessary fdb flush for test_configurable_drop_counters.
And also add sleep 3 sec after shutdown interface.

How did you verify/test it?

run test_configurable_drop_counters

Any platform specific information?

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

Documentation

[yejianquan]

@ZhaohuiS
Sorry to comment on the draft PR,
I just see there's another related fix pr of swss sonic-net/sonic-swss#2332 from your issue
Should we keep the unnecessary clear to qualify the swss fix?

[ZhaohuiS]

@ZhaohuiS Sorry to comment on the draft PR, I just see there's another related fix pr of swss Azure/sonic-swss#2332 from your issue Should we keep the unnecessary clear to qualify the swss fix?

@yejianquan Yes, I plan to hold this PR until we can verify 2332 [sonic-net/sonic-swss#2332] really fixes orchagent crash issue.