Improve test coverage for ConfObject in dag_run_schema (#10738)
Improve test coverage for ConfObject in dag_run_schema (#10738)

Adds test to verify that string can be passed to conf and ConfObject._deserialize works.
apache/airflow,cfei18/incubator-airflow,apache/airflow,bolkedebruin/airflow,bolkedebruin/airflow,mrkm4ntr/incubator-airflow,mrkm4ntr/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,DinoCow/airflow,dhuang/incubator-airflow,mistercrunch/airflow,Acehaidrey/incubator-airflow,apache/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,DinoCow/airflow,dhuang/incubator-airflow,nathanielvarona/airflow,apache/incubator-airflow,DinoCow/airflow,cfei18/incubator-airflow,DinoCow/airflow,lyft/incubator-airflow,sekikn/incubator-airflow,airbnb/airflow,nathanielvarona/airflow,mrkm4ntr/incubator-airflow,apache/airflow,lyft/incubator-airflow,nathanielvarona/airflow,sekikn/incubator-airflow,airbnb/airflow,mistercrunch/airflow,nathanielvarona/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,mistercrunch/airflow,apache/airflow,apache/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,dhuang/incubator-airflow,nathanielvarona/airflow,sekikn/incubator-airflow,dhuang/incubator-airflow,Acehaidrey/incubator-airflow,mrkm4ntr/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,sekikn/incubator-airflow,airbnb/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,nathanielvarona/airflow,bolkedebruin/airflow,airbnb/airflow,apache/airflow,cfei18/incubator-airflow