#31 Fixing Airflow env vars

The name of some of Airflow environment variables set in values.yaml, such as AIRFLOW_VAR_CORE__SERVICE__DATASET__HOST, are different from the ones osdu-airflow-lib is looking for (such as core__service__dataset__url that means the env var set in values.yaml must be named AIRFLOW_VAR_CORE__SERVICE__DATASET__URL).

I have noticed this error as well in greenfield deployments, which it is highly confusing as there is few log output to point to right direction of the error, this can be re-checked and corroborated on the osdu-ingestion-lib.

Closes #31 (closed)