private void sendRemoveMessages(List<ID> removals, List<String> reasons,
      Set<ID> oldIds) {
    Iterator<String> reason = reasons.iterator();
    for (ID mbr : removals) {
      // if olds not contains mbr then send remove request
      if (!oldIds.contains(mbr)) {
        RemoveMemberMessage<ID> response = new RemoveMemberMessage<>(mbr, mbr, reason.next());
        services.getMessenger().send(response);
      } else {
        reason.next();
      }
    }
  }
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