[test_po_cleanup] the new test failed due to dependence on the existing test

[AntonHryshchuk]

Description
The new test "test_po_cleanup_after_reload" failed if to run it after existed test "test_po_cleanup".
The existed test did the restart of swss docker and in the end, did cleanup by config reload, where the was a delay for bringup all critical processes.
When the new test was added, the cleanup was removed. #4554
As a result, the new test failed if to run the script "test_po_cleanup.py" with all tests.

Steps to reproduce the issue:

1. run the script "test_po_cleanup.py" with all tests

Describe the results you received:
From test output:

                pt_assert( 
                    False, 
                    'Processes "{}" had failures. Please check the logs'.format( 
>                       list(failed_processes.keys()) 
                    ) 
                ) 
E               Failed: Processes "['analyze_logs--<MultiAsicSonicHost>']" had failures. Please check the logs 

E               }, 
E               "msg": "failed dump port channel PortChannel1011 status return=1, out=, err=Error response from daemon: Container 727e53aab15cf80cafafc194407aa34b7122a000c04a02e9d0ddbbb469bd92d4 is not running\n" 
E           } 

    { 
        "name": "pc/test_po_cleanup.py::test_po_cleanup[...]", 
        "result": "passed" 
    }, 
    { 
        "name": "pc/test_po_cleanup.py::test_po_cleanup_after_reload[...]", 
        "result": "failed" 
    }, 
    { 
        "name": "pc/test_po_cleanup.py::test_po_cleanup_after_reload[...]", 
        "result": "error" 
    } 

Describe the results you expected:
The tests are pass