@Override
  public String[] getGroups() {
    String[] result = groups;
    if (result.length > 0) {
      // copy it for isolation
      String[] copy = new String[result.length];
      System.arraycopy(result, 0, copy, 0, result.length);
      result = copy;
    }
    return result;
  }
Method to create & send the ClientMembershipMessage to admin members. The message is sent
only if there are any admin members in the distribution system.

@param event describes a change in client membership
@param type type of event - one of ClientMembershipMessage.JOINED,
       ClientMembershipMessage.LEFT, ClientMembershipMessage.CRASHED
geode-core/src/main/java/org/apache/geode/internal/cache/AbstractCacheServer.java