Fix issue with test_syslog_rate_limit

[Staphylo]

Description of PR

There is a race condition in the rate-limit-host test code.
Changing the rate limit via the cli triggers hostcfgd to restart rsyslogd. However there is no wait to make sure this actually happens. This leads to some flakyness where loganalyzer.py would try to put a marker while the rsyslog systemd service is being restarted and crash.

Type of change

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

Back port request

• 201911
• 202012
• 202205
• 202305

Approach

What is the motivation for this PR?

Fix flaky test to enhance pass rate reliability.

How did you do it?

Reproduced on my testbed, investigated the issue, fixed the issue

How did you verify/test it?

Stressed the test overnight without further failure

[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/syslog/test_syslog_rate_limit.py:180:121: E501 line too long (124 > 120 characters)
tests/syslog/test_syslog_rate_limit.py:249:1: E302 expected 2 blank lines, found 1
tests/syslog/test_syslog_rate_limit.py:253:1: E302 expected 2 blank lines, found 1
tests/syslog/test_syslog_rate_limit.py:273:1: E302 expected 2 blank lines, found 1

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:

1. 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.
2. Ensure that the pre-commit package is installed:

sudo pip install pre-commit

3. Go to repository root folder
4. Install the pre-commit hooks:

pre-commit install

5. Use pre-commit to check staged file:

pre-commit

6. Alternatively, you can check committed files using:

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

[Staphylo]

@StormLiangMS

[StormLiangMS]

LGTM

[mssonicbld]

Cherry-pick PR to 202305: #10982