useFunctionsEmulator not working with region

### [REQUIRED] Describe your environment

* Operating System version: Windows 10
* Browser version: Chrome 79
* Firebase SDK version: 7.6.1
* Firebase Product: Functions

### [REQUIRED] Describe the problem

Emulator url will be ignored and call to `cloudfunctions.net` instead when setting region.
#### Relevant Code:

```javascript
firebase.functions().useFunctionsEmulator("http://localhost:5001");

// This will call to cloudfunctions.net
firebase.app().functions("asia-east2").httpsCallable();

// This will call to localhost
firebase.app().functions().httpsCallable();
```

Reproduce the issue with Firebase SDK 7.6.1 using the provided useFunctionsEmulator and regional functions calls on Windows 10. Compare the emulator and cloudfunctions.net routing; done when setting the asia-east2 region still sends the callable request to localhost:5001.

Written by the indexing model from the issue text.