**Apache Airflow version**: 2.0.0


**Kubernetes version (if you are using kubernetes)** (use `kubectl version`):

**Environment**:

- **Cloud provider or hardware configuration**:
- **OS** (e.g. from /etc/os-release):
- **Kernel** (e.g. `uname -a`):
- **Install tools**:
- **Others**:

**What happened**:

I have the following DAG:

```py
from datetime import datetime, timedelta

from airflow import DAG
from airflow.operators.bash_operator import BashOperator

with DAG(
    dag_id="sla_trigger",
    schedule_interval="* * * * *",
    start_date=datetime(2020, 2, 3),
) as dag:
    BashOperator(
        task_id="bash_task",
        bash_command="sleep 30",
        sla=timedelta(seconds=2),
    )

```

And in my understanding this dag should result in SLA miss every time it is triggered (every minute). However, after few minutes of running I don't see any SLA misses...

**What you expected to happen**:

I expect to see SLA if task takes longer than expected.

**How to reproduce it**:

Use the dag from above.

**Anything else we need to know**:

N/A

airflow/jobs/scheduler_job.py
TI.dag_id == dag.dag_id,
                TI.task_id == qry.c.task_id,
                TI.execution_date == qry.c.max_ti,
            )
            .all()
        )
        ts = timezone.utcnow()
        for ti in max_tis:
            task = dag.get_task(ti.task_id)
            if not isinstance(task.sla, timedelta):
                continue
            dttm = dag.following_schedule(ti.execution_date)
            while dttm < timezone.utcnow():
                following_schedule = dag.following_schedule(dttm)
                if following_schedule + task.sla < timezone.utcnow():
                    session.merge(
                        SlaMiss(task_id=ti.task_id, dag_id=ti.dag_id, execution_date=dttm, timestamp=ts)
                    )
                dttm = dag.following_schedule(dttm)
        session.commit()
        
        slas: List[SlaMiss] = (
            session.query(SlaMiss)
            .filter(SlaMiss.notification_sent == False, SlaMiss.dag_id == dag.dag_id)  
            .all()
        )
        
        if slas:  
            sla_dates: List[datetime.datetime] = [sla.execution_date for sla in slas]
            fetched_tis: List[TI] = (