Typo/grammar fix in a print statement.

git-svn-id: svn://bind10.isc.org/svn/bind10/trunk@1362 e5f2f494-b856-4b98-b285-d166d9295462

src/bin/usermgr/b10-cmdctl-usermgr.py.in

@@ -96,7 +96,7 @@ def main():
                 continue
 
             if username_exist(name, filename):
-                 print("use name already exist!")
+                 print("user name already exists!")
                  continue
 
             while True: