Fix 'Dangerous default value [] as argument' issue in tests\test_usage.py

[reactive-firewall]

CodeFactor found an issue: Dangerous default value [] as argument

It's currently on:
tests\test_usage.py:54

code should be something like:

def functionName(arg1=None, arg2=None):
    if arg1 is None:
        arg1 = [None]
    ...