Add portstat to debug FDB packet delay issue

[kperumalbfn]

Description of PR

In some fdb test runs, packets are not received by PTF server. To debug this issue, add DUT's portstat in the test log.

Type of change

Debug failures

Back port request

None

Approach

What is the motivation for this PR?

Add DUT portstat to debug any PTF server packet drop issues.

How did you do it?

Include DUT's portstat.

[linux-foundation-easycla]

• ✅ login: kperumalbfn / name: Kumaresh Perumal (1229c98, 3d0d7c7, 16f753d)
• ❌ The email address for the commit (4f9f28d, b6b835c) is not linked to the GitHub account, preventing the EasyCLA check. Consult this Help Article and GitHub Help to resolve. (To view the commit's email address, add .patch at the end of this PR page's URL.) For further assistance with EasyCLA, please submit a support request ticket.

[mssonicbld]

The pre-commit check detected issues in the files touched by this pull request.
The pre-commit check is a mandatory check, please fix detected issues.

Detailed pre-commit check results:
trim trailing whitespace.................................................Passed
fix end of files.........................................................Passed
check yaml...........................................(no files to check)Skipped
check for added large files..............................................Passed
check python ast.........................................................Passed
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

tests/fdb/test_fdb.py:195:121: E501 line too long (121 > 120 characters)

flake8...............................................(no files to check)Skipped
check conditional mark sort..........................(no files to check)Skipped

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