**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
):
                self.log.info(
                    "DAG %s already has %d active runs, not queuing any tasks for run %s",
                    dag.dag_id,
                    len(currently_active_runs),
                    dag_run.execution_date,
                )
                return 0
        self._verify_integrity_if_dag_changed(dag_run=dag_run, session=session)
        
        schedulable_tis, callback_to_run = dag_run.update_state(session=session, execute_callbacks=False)
        self._send_dag_callbacks_to_processor(dag_run, callback_to_run)
        
        
        
        
        return dag_run.schedule_tis(schedulable_tis, session)
    @provide_session
    def _verify_integrity_if_dag_changed(self, dag_run: DagRun, session=None):
        """Only run DagRun.verify integrity if Serialized DAG has changed since it is slow"""
        latest_version = SerializedDagModel.get_latest_version_hash(dag_run.dag_id, session=session)
        if dag_run.dag_hash == latest_version:
            self.log.debug("DAG %s not changed structure, skipping dagrun.verify_integrity", dag_run.dag_id)
            return
        dag_run.dag_hash = latest_version
        
        dag_run.dag = self.dagbag.get_dag(dag_id=dag_run.dag_id, session=session)
        
        dag_run.verify_integrity(session=session)
    def _send_dag_callbacks_to_processor(