[test_power_off_reboot.py] add missing fixture

[wenyiz2021]

Description of PR

this is to fix regression caused by #8646

cherry pick PR of #8646 is #8892 which already has the fix in current PR.

regression:

platform_tests/test_power_off_reboot.py::test_power_off_reboot[5-str2-7050cx3-acs-02] 
-------------------------------- live log call ---------------------------------
12:40:46 __init__.pytest_runtest_call             L0040 ERROR  | Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/_pytest/python.py", line 1464, in runtest
    self.ihook.pytest_pyfunc_call(pyfuncitem=self)
  File "/usr/local/lib/python2.7/dist-packages/pluggy/hooks.py", line 286, in __call__
    return self._hookexec(self, self.get_hookimpls(), kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pluggy/manager.py", line 93, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/usr/local/lib/python2.7/dist-packages/pluggy/manager.py", line 87, in <lambda>
    firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
  File "/usr/local/lib/python2.7/dist-packages/pluggy/callers.py", line 208, in _multicall
    return outcome.get_result()
  File "/usr/local/lib/python2.7/dist-packages/pluggy/callers.py", line 81, in get_result
    _reraise(*ex)  # noqa
  File "/usr/local/lib/python2.7/dist-packages/pluggy/callers.py", line 187, in _multicall
    res = hook_impl.function(*args)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/python.py", line 174, in pytest_pyfunc_call
    testfunction(**testargs)
  File "/azp/_work/78/s/tests/platform_tests/test_power_off_reboot.py", line 124, in test_power_off_reboot
    raise e
TypeError: 'function' object has no attribute '__getitem__'

after:

PASSED                                                                                                                                                                                       [ 50%]
platform_tests/test_power_off_reboot.py::test_power_off_reboot[15-str2-7050cx3-acs-02]

Summary:
Fixes # (issue)

Type of change

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

Back port request

• 201911
• 202012
• 202205

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

[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/platform_tests/test_power_off_reboot.py:34:61: F811 redefinition of unused 'conn_graph_facts' from line 5
tests/platform_tests/test_power_off_reboot.py:64:78: F811 redefinition of unused 'conn_graph_facts' from line 5

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>

[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/platform_tests/test_power_off_reboot.py:5:1: F401 'tests.common.fixtures.conn_graph_facts' imported but unused

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>

[ZhaohuiS]

LGTM