[AIRFLOW-2951] Update dag_run table end_date when state change (#3798)
[AIRFLOW-2951] Update dag_run table end_date when state change (#3798)

The existing airflow only change dag_run table end_date value when
a user teminate a dag in web UI. The end_date will not be updated
if airflow detected a dag finished and updated its state.

This commit add end_date update in DagRun's set_state function to
make up tho problem mentioned above.
owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow