CAS-based observe unit tests hangs

The hang occurs in when Task.WhenAll is called: https://github.com/couchbase/couchbase-net-client/blob/master/Src/Couchbase.IntegrationTests/CouchbaseBucket_KeyValue_Tests.cs#L314-L336

I am not sure why its only this test which hangs - its using the "observeConfig" - other tests that do similar things do not hang.