What problem are you facing?

While trying to connect to our mongodb at `mongo`, the driver tries to connect to localhost and times out:

```
> (node:8625) UnhandledPromiseRejectionWarning: MongoServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
at Timeout._onTimeout (/builds/seervision/main/svms/node_modules/mongodb/lib/sdam/topology.js:312:38)
at listOnTimeout (internal/timers.js:557:17)
at processTimers (internal/timers.js:500:7)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:8625) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see
https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode
). (rejection id: 1)
(node:8625) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
```

What driver and relevant dependency versions are you using?

Node `mongodb`  `4.7.0`

Steps to reproduce?

Have a mongo database running on any host but localhost. 

```
const mongo = require('mongodb');
const uri = "
[mongodb://172.17.0.2:27017]
"
client = new mongo.MongoClient(uri)
client.connect()
```