Use final to protect immutable ConnectionId

Mark non-test fields as private and final, and add a missing accessor.

Author: Steve Vaughan Jr

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java

@@ -1706,9 +1706,9 @@ private Connection getConnection(ConnectionId remoteId,
   @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
   @InterfaceStability.Evolving
   public static class ConnectionId {
-    InetSocketAddress address;
-    UserGroupInformation ticket;
-    final Class<?> protocol;
+    private final InetSocketAddress address;
+    private final UserGroupInformation ticket;
+    private final Class<?> protocol;
     private static final int PRIME = 16777619;
     private final int rpcTimeout;
     private final int maxIdleTime; //connections will be culled if it was idle for 

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/WritableRpcEngine.java

@@ -323,7 +323,7 @@ public <T> ProtocolProxy<T> getProxy(Class<T> protocol, long clientVersion,
       Client.ConnectionId connId, Configuration conf, SocketFactory factory)
       throws IOException {
     return getProxy(protocol, clientVersion, connId.getAddress(),
-        connId.ticket, conf, factory, connId.getRpcTimeout(),
+        connId.getTicket(), conf, factory, connId.getRpcTimeout(),
         connId.getRetryPolicy(), null, null);
   }