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**Apache Airflow version**: 2.0.0


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


**What happened**:

When I click on the "Triggered DAG" Operator Link in TriggerDagRunOperator, I am redirected with a relative link.

![Screen Shot 2021-03-08 at 4 28 16 PM](https://user-images.githubusercontent.com/5952735/110399833-61f00100-802b-11eb-9399-146bfcf8627c.png)

The redirect uses the HTML base URL and not the airflow base URL. This is only an issue if the URLs do not match.

**What you expected to happen**:

I expect the link to take me to the Triggered DAG tree view (default view) instead of the base url of the service hosting the webserver. 

**How to reproduce it**:

Create an airflow deployment where the HTML base url doesn't match the airflow URL. 




tests/utils/test_helpers.py
"""
        Test merge_dicts with recursive dict; two levels of nesting
        """
        dict1 = {'a': 1, 'r': {'a': 1, 'b': {'a': 1}}}
        dict2 = {'a': 1, 'r': {'c': 3, 'b': {'b': 1}}}
        merged = merge_dicts(dict1, dict2)
        assert merged == {'a': 1, 'r': {'a': 1, 'b': {'a': 1, 'b': 1}, 'c': 3}}
    def test_merge_dicts_recursive_right_only(self):
        """
        Test merge_dicts with recursive when dict1 doesn't have any nested dict
        """
        dict1 = {'a': 1}
        dict2 = {'a': 1, 'r': {'c': 3, 'b': 0}}
        merged = merge_dicts(dict1, dict2)
        assert merged == {'a': 1, 'r': {'b': 0, 'c': 3}}
    @conf_vars(
        {
            ("webserver", "dag_default_view"): "custom",
        }
    )
    def test_build_airflow_url_with_query(self):
        query = {"dag_id": "test_dag", "param": "key/to.encode"}
        url = build_airflow_url_with_query(query)
        assert url == "/custom?dag_id=test_dag&param=key%2Fto.encode"