@Override
  public boolean isListening() {
    return listening;
  }
Disconnects this agent from the distributed system. If this is a dedicated administration VM,
then the underlying connection to the distributed system is also closed.

@return true if this agent was disconnected as a result of the invocation
@see RemoteGemFireVM#disconnect
geode-core/src/main/java/org/apache/geode/internal/admin/remote/RemoteGfManagerAgent.java