How to handle java.lang.IllegalStateException at RealAppSyncCall.java:383

@cbommas
Hello.

We've caught exception very similar to issue #65 with similar stacktrace on executing a lot of mutations but on *AppSync 2.7.8*:

```
Fatal Exception: java.lang.IllegalStateException: Expected: TERMINATED, but found [ACTIVE, CANCELED]
at com.apollographql.apollo.internal.RealAppSyncCall.responseCallback(RealAppSyncCall.java:383)
at com.apollographql.apollo.internal.RealAppSyncCall.access$000(RealAppSyncCall.java:72)
at com.apollographql.apollo.internal.RealAppSyncCall$1.onResponse(RealAppSyncCall.java:272)
at com.amazonaws.mobileconnectors.appsync.InterceptorCallback.onResponse(InterceptorCallback.java:127)
at com.apollographql.apollo.internal.interceptor.ApolloCacheInterceptor$1$1.onResponse(ApolloCacheInterceptor.java:102)
at com.apollographql.apollo.internal.interceptor.ApolloParseInterceptor$1.onResponse(ApolloParseInterceptor.java:84)
at com.apollographql.apollo.internal.interceptor.ApolloServerInterceptor$1$1.onResponse(ApolloServerInterceptor.java:110)
at okhttp3.RealCall$AsyncCall.execute(RealCall.java:206)
at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:764)
```

Read RealAppSyncCall.java around line 383 and compare the report with issue #65. Reproduce the failure while executing many mutations against AppSync 2.7.8, using the supplied stack trace as the checkpoint. Done means the exception's cause and expected handling are identified and verified.

Written by the indexing model from the issue text.