Flowetl integration tests fail when airflow gives deprecation warnings

[greenape]

At the moment, because the check for whether a dag is running (https://github.com/Flowminder/FlowKit/blob/master/flowetl/tests/integration/test_full_pipeline.py#L32) looks for the word 'running', tests go entirely pear shaped if airflow warns about a deprecation because the warning message also includes the word 'running'.

We should probably move to calling the rest api, rather than using the cli for this.