cli: fix wrong error info when display ifconfig status (#324)

src/cli/README.md

@@ -236,6 +236,16 @@ Bring down the IPv6 interface.
 Done
 ```
 
+### ifconfig
+
+Show the status of the IPv6 interface.
+
+```bash
+> ifconfig
+down
+Done
+```
+
 ### ipaddr
 
 List all IPv6 addresses assigned to the Thread interface.

src/cli/cli.cpp

@@ -430,7 +430,7 @@ exit:
 
 void Interpreter::ProcessIfconfig(int argc, char *argv[])
 {
-    ThreadError error = kThreadError_Parse;
+    ThreadError error = kThreadError_None;
 
     if (argc == 0)
     {