Add error message when xfrin is run standalone.

git-svn-id: svn://bind10.isc.org/svn/bind10/trunk@1320 e5f2f494-b856-4b98-b285-d166d9295462

src/bin/xfrin/xfrin.py.in

@@ -438,6 +438,9 @@ if __name__ == '__main__':
         xfrind.startup()
     except KeyboardInterrupt:
         print("exit http server")
+    except isc.cc.session.SessionError as e:
+        print(e)
+        print('[b10-xfrin] Error happened! is the command channel daemon running?')
     except Exception as e:
         print(e)