Disable the Packet Filter.

    CLI example:

    .. code-block:: bash

        salt '*' pf.disable

def disable():
    '''
    Disable the Packet Filter.

    CLI example:

    .. code-block:: bash

        salt '*' pf.disable
    '''
    ret = {}
    result = __salt__['cmd.run_all']('pfctl -d',
                                     output_loglevel='trace',
                                     python_shell=False)

    if result['retcode'] == 0:
        ret = {'comment': 'pf disabled', 'changes': True}
    else:
        # If pf was already disabled the return code is also non-zero.
        # Don't raise an exception in that case.
        if result['stderr'] == 'pfctl: pf not enabled':
            ret = {'comment': 'pf already disabled', 'changes': False}
        else:
            raise CommandExecutionError(
                'Could not disable pf',
                info={'errors': [result['stderr']], 'changes': False}
            )

    return ret