[FAB-8240] Document Orderer.Addresses config setting

This changeset documents the `Orderer.Addresses` configuration parameter in
`configtx.yaml` and readthedocs.

Change-Id: Idbf35a2a3ba32f9db6ea6f33a1b214544c008ecd
Signed-off-by: luomin <luomin_tokyotech@hotmail.com>
Signed-off-by: Kostas Christids <kostas@christidis.io>

docs/source/ordering-service-faq.rst

@@ -91,6 +91,17 @@ Solo
 Kafka
 ~~~~~
 
+:Question:
+  **How do I remove a node from the ordering service?**
+
+:Answer:
+  This is a two step-process:
+
+  1. Add the node's certificate to the relevant orderer's MSP CRL to prevent peers/clients from connecting to it. 
+  2. Prevent the node from connecting to the Kafka cluster by leveraging standard Kafka access control measures such as TLS CRLs, or firewalling.
+
+..
+
 :Question:
   **I have never deployed a Kafka/ZK cluster before, and I want to use the
   Kafka-based ordering service. How do I proceed?**

sampleconfig/configtx.yaml

@@ -277,7 +277,11 @@ Orderer: &OrdererDefaults
     # Orderer Type: The orderer implementation to start.
     # Available types are "solo" and "kafka".
     OrdererType: solo
-
+
+    # Addresses here is a nonexhaustive list of orderers the peers and clients can 
+    # connect to. Adding/removing nodes from this list has no impact on their 
+    # participation in ordering. 
+    # NOTE: In the solo case, this should be a one-item list.
     Addresses:
         - 127.0.0.1:7050