[AIRFLOW-3306] Disable flask-sqlalchemy modification tracking. (#4146)
[AIRFLOW-3306] Disable flask-sqlalchemy modification tracking. (#4146)

By default, flask-sqlalchemy tracks model changes for its event system, which
adds some overhead. Since I don't think we're using the flask-sqlalchemy
event system, we should be able to turn off modification tracking and improve
performance.
mistercrunch/airflow,wileeam/airflow,sekikn/incubator-airflow,cfei18/incubator-airflow,wooga/airflow,Acehaidrey/incubator-airflow,wooga/airflow,artwr/airflow,nathanielvarona/airflow,fenglu-g/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,apache/airflow,bolkedebruin/airflow,danielvdende/incubator-airflow,wileeam/airflow,sekikn/incubator-airflow,apache/incubator-airflow,wooga/airflow,apache/airflow,adamhaney/airflow,fenglu-g/incubator-airflow,cfei18/incubator-airflow,r39132/airflow,fenglu-g/incubator-airflow,danielvdende/incubator-airflow,dhuang/incubator-airflow,spektom/incubator-airflow,lyft/incubator-airflow,artwr/airflow,DinoCow/airflow,Acehaidrey/incubator-airflow,artwr/airflow,artwr/airflow,DinoCow/airflow,jgao54/airflow,wooga/airflow,Acehaidrey/incubator-airflow,spektom/incubator-airflow,apache/airflow,cfei18/incubator-airflow,malmiron/incubator-airflow,adamhaney/airflow,lyft/incubator-airflow,apache/incubator-airflow,Fokko/incubator-airflow,sekikn/incubator-airflow,jgao54/airflow,cfei18/incubator-airflow,bolkedebruin/airflow,apache/incubator-airflow,cfei18/incubator-airflow,malmiron/incubator-airflow,mtagle/airflow,danielvdende/incubator-airflow,mrkm4ntr/incubator-airflow,mrkm4ntr/incubator-airflow,cfei18/incubator-airflow,malmiron/incubator-airflow,jgao54/airflow,airbnb/airflow,apache/airflow,mtagle/airflow,r39132/airflow,malmiron/incubator-airflow,airbnb/airflow,wileeam/airflow,bolkedebruin/airflow,sekikn/incubator-airflow,dhuang/incubator-airflow,apache/airflow,mtagle/airflow,jgao54/airflow,fenglu-g/incubator-airflow,mistercrunch/airflow,nathanielvarona/airflow,adamhaney/airflow,dhuang/incubator-airflow,DinoCow/airflow,Fokko/incubator-airflow,wileeam/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,mrkm4ntr/incubator-airflow,r39132/airflow,spektom/incubator-airflow,nathanielvarona/airflow,adamhaney/airflow,spektom/incubator-airflow,Acehaidrey/incubator-airflow,DinoCow/airflow,bolkedebruin/airflow,Fokko/incubator-airflow,Fokko/incubator-airflow,mistercrunch/airflow,airbnb/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,airbnb/airflow,apache/incubator-airflow,lyft/incubator-airflow,r39132/airflow,nathanielvarona/airflow,mtagle/airflow,nathanielvarona/airflow,dhuang/incubator-airflow,mrkm4ntr/incubator-airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,lyft/incubator-airflow