[test_tunnel_memory_leak] The memory leak check mechanism need to be updated

[echuawu]

Description
The test logic is flowed. The test tries to trigger tunnel packet handler and check the memory increase. However it checks swss docker using "docker state swss --no-stream". This considers the memory of swss docker + all processes. Since the while docker is considered there might be some temporal memory increased due to usage by docker subsystem as you can see in the running log.
Overall, the test needs to be more deterministic in figuring out the memory leak and not use very generic mechanism as used today.

Steps to reproduce the issue:

1. Run the script at dualtor-64 topology.

Describe the results you received:

1. Memory usage exceeds the threshold

Describe the results you expected:

1. The test needs to be more deterministic in figuring out the memory leak and not use very generic mechanism as used today.

Additional information you deem important:

**Output of `show version`:**

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

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[liat-grozovik]

@yxieca are you aware of someone going to fix this issue? no assignee.
if not, i believe we should go a head and merge to skip based on github issue

[bingwang-ms]

@ZhaohuiS Can you please help take a look at this issue?