Certificate Verify Failed on ECSCluster

**Description**
An attempt was made to create a Dask cluster on ECS with ECSCluster. I am receiving an SSL certificate verification error. Typically I solve this by providing the session created by aibotocore with the parameter "use_ssl=False". I have done so with s3fs in the past.

```
s3fs.S3FileSystem(use_ssl=False)
```

That doesn't seem to be an option so I tried setting the security argument to False as provided in the documentation but that also does not seem to work.

**Example**
```python
from dask_cloudprovider.aws import ECSCluster

cluster = ECSCluster(cluster_arn="my cluster", security=False)
```

**What happened**:

Traceback (most recent call last):
```
File "/home/wfclark5/miniconda3/envs/ops_dev/lib/python3.6/site-packages/aiohttp/connector.py", line 985, in _wrap_create_connection
return await self._loop.create_connection(*args, **kwargs) # type: ignore[return-value] # noqa
File "/home/wfclark5/miniconda3/envs/ops_dev/lib/python3.6/asyncio/base_events.py", line 824, in create_connection
sock, protocol_factory, ssl, server_hostname)
File "/home/wfclark5/miniconda3/envs/ops_dev/lib/python3.6/asyncio/base_events.py", line 850, in _create_connection_transport
yield from waiter
File "/home/wfclark5/miniconda3/envs/ops_dev/lib/python3.6/asyncio/sslproto.py", line 505, in data_received
ssldata, appdata = self._sslpipe.feed_ssldata(data)
File "/home/wfclark5/miniconda3/envs/ops_dev/lib/python3.6/asyncio/sslproto.py", line 201, in feed_ssldata
self._sslobj.do_handshake()
File "/home/wfclark5/miniconda3/envs/ops_dev/lib/python3.6/ssl.py", line 689, in do_handshake
self._sslobj.do_handshake()
ssl.SSLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:852)
```
**What you expected to happen**:

Make an attempt to create a Dask cluster on ECS.

**Anything else we need to know?**:

Behind a firewall that doesn't allow for SSL, so disabling SSL is a requirement for local development.

**Environment**:

- Dask version: '2021.03.0'
- Dask Cloud Provider version: '0.5.0'
- Python version: 3.6.13
- Operating System: Ubuntu-18.04 (local)
- Install method (conda, pip, source): pip