void processViewAckMessage(ViewAckMessage<ID> m) {
    if (isStopping) {
      return;
    }

    if (m.isPrepareAck()) {
      prepareProcessor.processViewResponse(m.getViewId(), m.getSender(), m.getAlternateView());
    } else {
      viewProcessor.processViewResponse(m.getViewId(), m.getSender(), m.getAlternateView());
    }
  }
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