private SettableFuture<Boolean> createDefaultWaitForAmRegistryFuture() {
    SettableFuture<Boolean> noWait = SettableFuture.create();
    noWait.set(true); // By default, do not wait.
    return noWait;
  }
This class is needed for writing junit tests. For testing the multi-session
use case from hive server 2, we need a session simulation.
ql/src/test/org/apache/hadoop/hive/ql/exec/tez/SampleTezSessionState.java