Convert state arguments to ExternalTaskSensor to list (#12794)
Convert state arguments to ExternalTaskSensor to list (#12794)

Without this if you pass a tuple or a set etc things would break.
nathanielvarona/airflow,cfei18/incubator-airflow,DinoCow/airflow,mistercrunch/airflow,nathanielvarona/airflow,apache/incubator-airflow,cfei18/incubator-airflow,sekikn/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,mistercrunch/airflow,dhuang/incubator-airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,apache/incubator-airflow,dhuang/incubator-airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,nathanielvarona/airflow,sekikn/incubator-airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,apache/incubator-airflow,bolkedebruin/airflow,bolkedebruin/airflow,airbnb/airflow,apache/airflow,DinoCow/airflow,apache/airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,airbnb/airflow,danielvdende/incubator-airflow,apache/incubator-airflow,mistercrunch/airflow,airbnb/airflow,nathanielvarona/airflow,dhuang/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,apache/airflow,nathanielvarona/airflow,dhuang/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,apache/airflow,cfei18/incubator-airflow,DinoCow/airflow,DinoCow/airflow,apache/airflow,airbnb/airflow,lyft/incubator-airflow,sekikn/incubator-airflow,mistercrunch/airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,sekikn/incubator-airflow