**Apache Airflow version**:
1.10.14 and 1.10.8. 

**Environment**:
Python 3.6 and Airflow 1.10.14 on sqllite,

**What happened**:

Nested jinja templates do not consistently render when running tasks. TI run rendering behavior also differs from airflow UI and airflow render cli. 

**What you expected to happen**:

Airflow should render nested jinja templates consistently and completely across each interface. Coming from airflow 1.8.2, this used to be the case.

<!-- What do you think went wrong? -->

This regression may have been introduced in 1.10.6 with a refactor of BaseOperator templating functionality. 
https://github.com/apache/airflow/pull/5461

Whether or not a nested layer renders seems to differ based on which arg is being templated in an operator and perhaps order. Furthermore, it seems like the render cli and airflow ui each apply TI.render_templates() a second time, creating inconsistency in what nested templates get rendered.

There may be bug in the way BaseOperator.render_template() observes/caches templated fields

**How to reproduce it**:
From the most basic airflow setup

nested_template_bug.py


```
from datetime import datetime
from airflow import DAG
from airflow.operators.python_operator import PythonOperator

with DAG("nested_template_bug", start_date=datetime(2021, 1, 1)) as dag:

    arg0 = 'level_0_{{task.task_id}}_{{ds}}'
    kwarg1 = 'level_1_{{task.op_args[0]}}'

    def print_fields(arg0, kwarg1):
        print(f'level 0 arg0: {arg0}')
        print(f'level 1 kwarg1: {kwarg1}') 

    nested_render = PythonOperator(
        task_id='nested_render',
        python_callable=print_fields,
        op_args=[arg0, ],
        op_kwargs={
            'kwarg1': kwarg1,
        },
    )
```

```
> airflow test c

level 0 arg0: level_0_nested_render_2021-01-01
level 1 kwarg1: level_1_level_0_{{task.task_id}}_{{ds}}

> airflow render nested_template_bug nested_render 2021-01-01

# ----------------------------------------------------------
# property: op_args
# ----------------------------------------------------------
['level_0_nested_render_2021-01-01']

# ----------------------------------------------------------
# property: op_kwargs
# ----------------------------------------------------------
{'kwarg1': 'level_1_level_0_nested_render_2021-01-01'}
```
airflow/models/taskinstance.py
"""
        Forces the task instance's state to FAILED in the database.
        :param session: SQLAlchemy ORM Session
        :type session: Session
        """
        self.log.error("Recording the task instance as FAILED")
        self.state = State.FAILED
        session.merge(self)
        session.commit()
    @provide_session
    def refresh_from_db(self, session=None, lock_for_update=False) -> None:
        """
        Refreshes the task instance from the database based on the primary key
        :param session: SQLAlchemy ORM Session
        :type session: Session
        :param lock_for_update: if True, indicates that the database should
            lock the TaskInstance (issuing a FOR UPDATE clause) until the
            session is committed.
        :type lock_for_update: bool
        """
        self.log.debug("Refreshing TaskInstance %s from DB", self)
        qry = session.query(TaskInstance).filter(
            TaskInstance.dag_id == self.dag_id,
            TaskInstance.task_id == self.task_id,
            TaskInstance.run_id == self.run_id,
        )
        if lock_for_update:
            ti: Optional[TaskInstance] = qry.with_for_update().first()
        else:
            ti = qry.first()