private void ackView(InstallViewMessage<ID> m) {
    if (!playingDead && m.getView().contains(m.getView().getCreator())) {
      services.getMessenger()
          .send(new ViewAckMessage<>(m.getSender(), m.getView().getViewId(), m.isPreparing()));
    }
  }
Transitions this member into the coordinator role. This must be invoked under a synch on
viewInstallationLock that was held at the time the decision was made to become coordinator so
that the decision is atomic with actually becoming coordinator.

@param oldCoordinator may be null
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/membership/GMSJoinLeave.java