Return all available boot services

    CLI Example:

    .. code-block:: bash

        salt '*' service.get_all

def get_all():
    '''
    Return all available boot services

    CLI Example:

    .. code-block:: bash

        salt '*' service.get_all
    '''
    ret = set()
    lines = glob.glob('/etc/init.d/*')
    for line in lines:
        service = line.split('/etc/init.d/')[1]
        # Remove README.  If it's an enabled service, it will be added back in.
        if service != 'README':
            ret.add(service)
    return sorted(ret | set(get_enabled()))