Firestore + Auth emulators -> INVALID_REFRESH_TOKEN

### Environment

* Android Studio version: 2020.3.1 Beta 3
* Firebase Component: Firestore + Auth emulators
* Component version: Firestore version 23.0.1 // Firebase-Auth version 21.0.1
* Running on macOS 10.15.7
* firebase CLI version 9.12.1

### Problem
After a while, around 60 minutes (token expiration time) Firestore is unable to properly authenticate when using local emulators for both Firestore and Firebase-Auth.

### Expected behaviour:
The token should be automatically refreshed and access to Firestore should be allowed.

#### Steps to reproduce:

1. Run firestore + auth emulators (optionally enable security rules to allow authenticated queries)
2. Set up an android project and call 'useEmulator' methods on both FirebaseFirestore and AuthUI pointing to "10.0.2.2:8080" and "10.0.2.2:9099" (see settings on the next section)
3. Use FirebaseUI to handle login
3. On the main activity just trigger any method that uses Firestore
4. After a successful connection, kill the app and wait for the token to expire (without closing the emulators)
5. Open the app again and do not manually reauthenticate, just check FirebaseAuth.currentUser != null and verify that it's not null (which will be if step 3 succeeded), wait for the main activity to load and Firestore will throw an error and fail to connect due to INVALID_REFRESH_TOKEN

#### Relevant Code:

Firestore settings:
```
val firestore = FirebaseFirestore.getInstance()
firestore.useEmulator("10.0.2.2", 8080)

val settings = FirebaseFirestoreSettings.Builder()
.setPersistenceEnabled(false)
.build()
firestore.firestoreSettings = settings
```

Firebase Auth / UI settings:
```
AuthUI.getInstance().useEmulator("10.0.2.2", 9099)
val providers = arrayListOf(
AuthUI.IdpConfig.EmailBuilder().build(),
AuthUI.IdpConfig.GoogleBuilder().build())

launcher.launch(
AuthUI.getInstance()
.createSignInIntentBuilder()
.setIsSmartLockEnabled(false)
.setAvailableProviders(providers)
.build())
```

This is the exception thrown:

```
W/Firestore: (23.0.1) [FirestoreCallCredentials]: Failed to get token: com.google.firebase.FirebaseException: An internal error has occurred. [ INVALID_REFRESH_TOKEN ].
W/Firestore: (23.0.1) [WatchStream]: (1a1b32e) Stream closed with status: Status{code=UNAUTHENTICATED, description=null, cause=com.google.firebase.FirebaseException: An internal error has occurred. [ INVALID_REFRESH_TOKEN ]
at com.google.android.gms.internal.firebase-auth-api.zzto.zza(com.google.firebase:firebase-auth@@21.0.1:4)
at com.google.android.gms.internal.firebase-auth-api.zzuw.zza(com.google.firebase:firebase-auth@@21.0.1:9)
at com.google.android.gms.internal.firebase-auth-api.zzux.zzl(com.google.firebase:firebase-auth@@21.0.1:1)
at com.google.android.gms.internal.firebase-auth-api.zzuu.zzk(com.google.firebase:firebase-auth@@21.0.1:25)
at com.google.android.gms.internal.firebase-auth-api.zztl.zzh(com.google.firebase:firebase-auth@@21.0.1:1)
at com.google.android.gms.internal.firebase-auth-api.zzom.zza(com.google.firebase:firebase-auth@@21.0.1:2)
at com.google.android.gms.internal.firebase-auth-api.zzvb.zza(com.google.firebase:firebase-auth@@21.0.1:23)
at com.google.android.gms.internal.firebase-auth-api.zzul.zzf(com.google.firebase:firebase-auth@@21.0.1:4)
at com.google.android.gms.internal.firebase-auth-api.zzpt.zzp(com.google.firebase:firebase-auth@@21.0.1:4)
at com.google.android.gms.internal.firebase-auth-api.zztp.zzk(com.google.firebase:firebase-auth@@21.0.1:5)
at com.google.android.gms.internal.firebase-auth-api.zzqr.zzd(com.google.firebase:firebase-auth@@21.0.1:3)
at com.google.android.gms.internal.firebase-auth-api.zzqq.accept(Unknown Source:6)
at com.google.android.gms.common.api.internal.zacj.doExecute(com.google.android.gms:play-services-base@@17.1.0:2)
at com.google.android.gms.common.api.internal.zaf.zac(com.google.android.gms:play-services-base@@17.1.0:6)
at com.google.android.gms.common.api.internal.GoogleApiManager$zaa.zac(com.google.android.gms:play-services-base@@17.1.0:167)
at com.google.android.gms.common.api.internal.GoogleApiManager$zaa.zab(com.google.android.gms:play-services-base@@17.1.0:139)
at com.google.android.gms.common.api.internal.GoogleApiManager$zaa.zaa(com.google.android.gms:play-services-base@@17.1.0:105)
at com.google.android.gms.common.api.internal.GoogleApiManager.handleMessage(com.google.android.gms:play-services-base@@17.1.0:145)
at android.os.Handler.dispatchMessage(Handler.java:102)
at com.google.android.gms.internal.base.zar.dispatchMessage(com.google.android.gms:play-services-base@@17.1.0:8)
at android.os.Looper.loop(Looper.java:193)
at android.os.HandlerThread.run(HandlerThread.java:65)
}.
(23.0.1) [OnlineStateTracker]: Could not reach Cloud Firestore backend. Connection failed 1 times. Most recent error: Status{code=UNAUTHENTICATED, description=null, cause=com.google.firebase.FirebaseException: An internal error has occurred. [ INVALID_REFRESH_TOKEN ]
at com.google.android.gms.internal.firebase-auth-api.zzto.zza(com.google.firebase:firebase-auth@@21.0.1:4)
at com.google.android.gms.internal.firebase-auth-api.zzuw.zza(com.google.firebase:firebase-auth@@21.0.1:9)
at com.google.android.gms.internal.firebase-auth-api.zzux.zzl(com.google.firebase:firebase-auth@@21.0.1:1)
at com.google.android.gms.internal.firebase-auth-api.zzuu.zzk(com.google.firebase:firebase-auth@@21.0.1:25)
at com.google.android.gms.internal.firebase-auth-api.zztl.zzh(com.google.firebase:firebase-auth@@21.0.1:1)
at com.google.android.gms.internal.firebase-auth-api.zzom.zza(com.google.firebase:firebase-auth@@21.0.1:2)
at com.google.android.gms.internal.firebase-auth-api.zzvb.zza(com.google.firebase:firebase-auth@@21.0.1:23)
at com.google.android.gms.internal.firebase-auth-api.zzul.zzf(com.google.firebase:firebase-auth@@21.0.1:4)
at com.google.android.gms.internal.firebase-auth-api.zzpt.zzp(com.google.firebase:firebase-auth@@21.0.1:4)
at com.google.android.gms.internal.firebase-auth-api.zztp.zzk(com.google.firebase:firebase-auth@@21.0.1:5)
at com.google.android.gms.internal.firebase-auth-api.zzqr.zzd(com.google.firebase:firebase-auth@@21.0.1:3)
at com.google.android.gms.internal.firebase-auth-api.zzqq.accept(Unknown Source:6)
at com.google.android.gms.common.api.internal.zacj.doExecute(com.google.android.gms:play-services-base@@17.1.0:2)
at com.google.android.gms.common.api.internal.zaf.zac(com.google.android.gms:play-services-base@@17.1.0:6)
at com.google.android.gms.common.api.internal.GoogleApiManager$zaa.zac(com.google.android.gms:play-services-base@@17.1.0:167)
at com.google.android.gms.common.api.internal.GoogleApiManager$zaa.zab(com.google.android.gms:play-services-base@@17.1.0:139)
at com.google.android.gms.common.api.internal.GoogleApiManager$zaa.zaa(com.google.android.gms:play-services-base@@17.1.0:105)
at com.google.android.gms.common.api.internal.GoogleApiManager.handleMessage(com.google.android.gms:play-services-base@@17.1.0:145)
at android.os.Handler.dispatchMessage(Handler.java:102)
at com.google.android.gms.internal.base.zar.dispatchMessage(com.google.android.gms:play-services-base@@17.1.0:8)
at android.os.Looper.loop(Looper.java:193)
at android.os.HandlerThread.run(HandlerThread.java:65)
}
This typically indicates that your device does not have a healthy Internet connection at the moment. The client will operate in offline mode until it is able to successfully connect to the backend.
W/System: Ignoring header X-Firebase-Locale because its value was null.
```