**Description**

In similar fashion to https://github.com/apache/airflow/pull/4083, it would be helpful for Airflow to reattach itself to the ECS Task rather than letting another instance to start. However, instead of making this the default behavior, it would be better to use a `reattach` flag.

**Use case / motivation**

Allow Airflow the option to reattach to an existing ECS task when a restart happens, which would avoid having "rogue" tasks.
airflow/providers/amazon/aws/operators/ecs.py
super().__init__(**kwargs)
        self.aws_conn_id = aws_conn_id
        self.region_name = region_name
        self.task_definition = task_definition
        self.cluster = cluster
        self.overrides = overrides
        self.launch_type = launch_type
        self.group = group
        self.placement_constraints = placement_constraints
        self.placement_strategy = placement_strategy
        self.platform_version = platform_version
        self.network_configuration = network_configuration
        self.tags = tags
        self.awslogs_group = awslogs_group
        self.awslogs_stream_prefix = awslogs_stream_prefix
        self.awslogs_region = awslogs_region
        self.propagate_tags = propagate_tags
        if self.awslogs_region is None:
            self.awslogs_region = region_name
        self.hook: Optional[AwsBaseHook] = None
        self.client: Optional[ECSProtocol] = None
        self.arn: Optional[str] = None
    def execute(self, context):
        self.log.info(
            'Running ECS Task - Task definition: %s - on cluster %s', self.task_definition, self.cluster
        )
        self.log.info('ECSOperator overrides: %s', self.overrides)
        self.client = self.get_hook().get_conn()
        run_opts = {
            'cluster': self.cluster,