**Apache Airflow version**: 1.10.12


**Kubernetes version (if you are using kubernetes)** (use `kubectl version`): 1.16.9

**Environment**: 

- **Cloud provider or hardware configuration**: AWS
- **OS** (e.g. from /etc/os-release): 
- **Kernel** (e.g. `uname -a`): 
- **Install tools**: Docker image running in k8s Pods
- **Others**: Rancher-provisioned k8s clusters

**What happened**:

After configuring the latest version of the Elasticsearch backport provider as my log handler via `config/airflow_local_settings.py` resulted in an error on the webserver when trying to read logs from Elasticsearch

```
[2020-10-12 21:02:00,487] {app.py:1892} ERROR - Exception on /get_logs_with_metadata [GET]
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/usr/local/lib/python3.7/site-packages/airflow/www_rbac/decorators.py", line 121, in wrapper
    return f(self, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/flask_appbuilder/security/decorators.py", line 109, in wraps
    return f(self, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/airflow/www_rbac/decorators.py", line 56, in wrapper
    return f(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/airflow/utils/db.py", line 74, in wrapper
    return func(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/airflow/www_rbac/views.py", line 733, in get_logs_with_metadata
    logs, metadata = _get_logs_with_metadata(try_number, metadata)
  File "/usr/local/lib/python3.7/site-packages/airflow/www_rbac/views.py", line 724, in _get_logs_with_metadata
    logs, metadatas = handler.read(ti, try_number, metadata=metadata)
  File "/usr/local/lib/python3.7/site-packages/airflow/utils/log/file_task_handler.py", line 194, in read
    logs[i] += log
TypeError: can only concatenate str (not "list") to str
```

Here is the relevant section of my customized `airflow_local_settings.py` file with the updated Elasticsearch handler from the backport provider:
```
...
    elif ELASTICSEARCH_HOST:
        ELASTICSEARCH_LOG_ID_TEMPLATE: str = conf.get('elasticsearch', 'LOG_ID_TEMPLATE')
        ELASTICSEARCH_END_OF_LOG_MARK: str = conf.get('elasticsearch', 'END_OF_LOG_MARK')
        ELASTICSEARCH_FRONTEND: str = conf.get('elasticsearch', 'frontend')
        ELASTICSEARCH_WRITE_STDOUT: bool = conf.getboolean('elasticsearch', 'WRITE_STDOUT')
        ELASTICSEARCH_JSON_FORMAT: bool = conf.getboolean('elasticsearch', 'JSON_FORMAT')
        ELASTICSEARCH_JSON_FIELDS: str = conf.get('elasticsearch', 'JSON_FIELDS')

        ELASTIC_REMOTE_HANDLERS: Dict[str, Dict[str, Union[str, bool]]] = {
            'task': {
                'class': 'airflow.providers.elasticsearch.log.es_task_handler.ElasticsearchTaskHandler',
                'formatter': 'airflow',
                'base_log_folder': str(os.path.expanduser(BASE_LOG_FOLDER)),
                'log_id_template': ELASTICSEARCH_LOG_ID_TEMPLATE,
                'filename_template': FILENAME_TEMPLATE,
                'end_of_log_mark': ELASTICSEARCH_END_OF_LOG_MARK,
                'host': ELASTICSEARCH_HOST,
                'frontend': ELASTICSEARCH_FRONTEND,
                'write_stdout': ELASTICSEARCH_WRITE_STDOUT,
                'json_format': ELASTICSEARCH_JSON_FORMAT,
                'json_fields': ELASTICSEARCH_JSON_FIELDS
            },
        }

        LOGGING_CONFIG['handlers'].update(ELASTIC_REMOTE_HANDLERS)
...
```

**What you expected to happen**:

Airflow's web UI properly displays the logs from Elasticsearch

**How to reproduce it**:
Configure custom logging via `config/airflow_local_settings.py` to `airflow.providers.elasticsearch.log.es_task_handler.ElasticsearchTaskHandler` and set the `logging_config_class` in `airflow.cfg`

When a task has been run, try to view its logs in the web UI and check the webserver logs to see the error above

provider_packages/refactor_provider_packages.py
and it basically does nothing even if you do. And it's bad because it does not initialize
        LoggingMixin (BaseHook derives from LoggingMixin). And it is the main reason why Hook
        logs are not working as they are supposed to sometimes:
        .. code-block:: python
            class LoggingMixin(object):
                \"\"\"
                Convenience super-class to have a logger configured with the class name
                \"\"\"
                def __init__(self, context=None):
                    self._set_context(context)
        There are two Hooks in 1.10 that call super.__init__ :
        .. code-block:: python
               super(CloudSqlDatabaseHook, self).__init__(source=None)
               super(MongoHook, self).__init__(source='mongo')
        Not that it helps with anything because init in BaseHook does nothing. So we remove
        the super().init() in Hooks when backporting to 1.10.
        Example diff generated:
        .. code-block:: diff
            --- ./airflow/providers/apache/druid/hooks/druid.py
            +++ ./airflow/providers/apache/druid/hooks/druid.py
            @@ -49,7 +49,7 @@
                         timeout=1,
                         max_ingestion_time=None):
            -        super().__init__()
            +
                     self.druid_ingest_conn_id = druid_ingest_conn_id
                     self.timeout = timeout
                     self.max_ingestion_time = max_ingestion_time
        """
        def remove_super_init_call_modifier(node: LN, capture: Capture, filename: Filename) -> None: