python: Use pytest normal mode
    
    We have too many tests to use verbose mode. If verbose more is needed it
    can be enabled using:
    
        tox -e py36 tests/python_test.py -- -vv
    
    Or using environment variable:
    
        export PYTEST_ADDOPTS=-vv
    
    Signed-off-by: Nir Soffer <nsoffer@redhat.com>