private void startLocatorPreferredCoordinators(VM vm0, int port) {
    try {
      System.setProperty(InternalLocator.LOCATORS_PREFERRED_AS_COORDINATORS, "true");

      Properties locProps1 = new Properties();
      locProps1.setProperty(MCAST_PORT, "0");
      locProps1.setProperty(LOG_LEVEL, logger.getLevel().name());
      addDSProps(locProps1);

      startLocator(vm0, locProps1, port);
    } finally {
      System.clearProperty(InternalLocator.LOCATORS_PREFERRED_AS_COORDINATORS);
    }
  }
a locator is restarted twice with a server and ends up in a split-brain
geode-core/src/distributedTest/java/org/apache/geode/distributed/LocatorDUnitTest.java