
**Apache Airflow version**:
2.0.1

**Environment**:

- **OS**: Linux Mint 19.2 
- **Kernel**: 5.5.0-050500-generic #202001262030 SMP Mon Jan 27 01:33:36 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

**What happened**:

Seems that pagination doesn't work. I filter DAGs by tags and get too many results to get them at one page. When I click second page I'm redirected to the first one (actually, it doesn't matter if I click second, last or any other - I'm always getting redirected to the first one).

**What you expected to happen**:

I expect to be redirected to the correct page when I click number on the bottom of the page.

**How to reproduce it**:
1. Create a lot of DAGs with the same tag
2. Filter by tag
3. Go to the next page in the pagination bar

**Implementation example**:



```
from airflow import DAG
from airflow.utils.dates import days_ago
for i in range(200):
    name = 'test_dag_' + str(i)
    dag = DAG(
        dag_id=name,
        schedule_interval=None,
        start_date=days_ago(2),
        tags=['example1'],
    )
    globals()[name] = dag
```

airflow/www/views.py
"""Get Dag as duration graph."""
        default_dag_run = conf.getint('webserver', 'default_dag_run_display_number')
        dag_id = request.args.get('dag_id')
        try:
            dag = current_app.dag_bag.get_dag(dag_id)
        except airflow.exceptions.SerializedDagNotFound:
            dag = None
        base_date = request.args.get('base_date')
        num_runs = request.args.get('num_runs', default=default_dag_run, type=int)
        if dag is None:
            flash(f'DAG "{dag_id}" seems to be missing.', "error")
            return redirect(url_for('Airflow.index'))
        if base_date:
            base_date = timezone.parse(base_date)
        else:
            base_date = dag.get_latest_execution_date() or timezone.utcnow()
        dates = dag.date_range(base_date, num=-abs(num_runs))
        min_date = dates[0] if dates else timezone.utc_epoch()
        root = request.args.get('root')
        if root: