Locking Preferences in Mozilla
Solution 1:
Your file should start with double //, and I think the correct term is lockPref. The correct contents of your file should be;
//
lockPref("security.enable_ssl3", false);
Also, you should save this file in the root of the installation directory and modify local-settings.js to load the file.
pref("general.config.filename", "test.js");