Read providers from configfile and de-duplicate it.

def config_prov(config):
    """Read providers from configfile and de-duplicate it."""
    try:
        providers = [e.strip() for e in (config['info']
                                         ['providers']).split(',')]
    except KeyError as e:
        print("Error reading config item: {}".format(e))
        sys.exit()
    providers = list(OrderedDict.fromkeys(providers))
    return providers