Make task ID on legend have enough width and width of line chart to be 100%.  (#15915)
Make task ID on legend have enough width and width of line chart to be 100%.  (#15915)

* Make task ID on legend have enough width and width of line chart to be 100%.

* Make task ID on legend have enough width and width of line chart to be 100%.

* Fix pylint errors.
Acehaidrey/incubator-airflow,mistercrunch/airflow,dhuang/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,apache/airflow,Acehaidrey/incubator-airflow,dhuang/incubator-airflow,apache/airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,lyft/incubator-airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,apache/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,dhuang/incubator-airflow,Acehaidrey/incubator-airflow,mistercrunch/airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,cfei18/incubator-airflow,lyft/incubator-airflow,apache/airflow,apache/airflow,cfei18/incubator-airflow,bolkedebruin/airflow,nathanielvarona/airflow,mistercrunch/airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,bolkedebruin/airflow,dhuang/incubator-airflow,apache/incubator-airflow,Acehaidrey/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,bolkedebruin/airflow,apache/incubator-airflow,apache/incubator-airflow,cfei18/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,bolkedebruin/airflow,lyft/incubator-airflow,lyft/incubator-airflow