Validate /etc/resolv.conf in each docker container

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/dns/test_dns_resolv_conf.py:79:21: E128 continuation line under-indented for visual indent flake8...............................................(no files to check)Skipped check conditional mark sort..........................(no files to check)Skipped

To run the pre-commit checks locally, you can follow below steps:

Ensure that default python is python3. In sonic-mgmt docker container, default python is python2. You can run the check by activating the python3 virtual environment in sonic-mgmt docker container or outside of sonic-mgmt docker container.
Ensure that the pre-commit package is installed:
```
sudo pip install pre-commit
```
Go to repository root folder
Install the pre-commit hooks:
```
pre-commit install
```
Use pre-commit to check staged file:
```
pre-commit
```

Alternatively, you can check committed files using:

pre-commit run --from-ref <commit_id> --to-ref <commit_id>

sonic-net / sonic-mgmt

Validate /etc/resolv.conf in each docker container #13559

Description of PR

Type of change

Back port request

Approach

What is the motivation for this PR?

How did you do it?

How did you verify/test it?

Any platform specific information?

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

Documentation