NullPointerException on ServiceFuture.cancel()

[weidongxu-microsoft]

ServiceFuture.fromBody(Completable, ServiceCallback) does not assign value to subscription class variable.
https://github.com/Azure/autorest-clientruntime-for-java/blob/master/client-runtime/src/main/java/com/microsoft/rest/ServiceFuture.java#L129-L150

Then ServiceFuture.cancel() calls subscription.unsubscribe() which produces NullPointerException, as subscription is null.

The correct code should be serviceFuture.subscription = completable.subscribe(...

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Temporary workaround, avoid calling ServiceFuture.fromBody(Completable, ServiceCallback). Use other factory method e.g. ServiceFuture.fromBody(Observable, ServiceCallback).