@Override
  public final void preTearDown() throws Exception {
    disconnectAllFromDS();
    invokeInEveryVM(() -> cache = null);
  }
This is the bugtest for bug no. 36738. When Object of class ClientUpdateMessage gets deserialized
it thows NPE if region mentioned in the ClientUpdateMessage is not present on the node. The test
performs following operations 1. Create server1 and HARegion. 2. Perform put operations on
HARegion with the value as ClientUpdateMessage. 3. Create server2 and HARegion in it so that GII
will happen. 4. Perform get operations from server2.
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/tier/sockets/HABug36738DUnitTest.java