When C-Channel isn't started up, make BigTool exit directly.

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/f2f200910@199 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/bigtool/bigtool.py

@@ -39,7 +39,7 @@ class BigTool(Cmd):
             self.cc.group_subscribe("ConfigManager")
         except ISC.CC.SessionError:
             print("Failed to create cchannel session")
-            return
+            exit()
 
     def validate_cmd(self, cmd):
         if not cmd.module in self.modules: