mocha silently skips bad test files

[Richard Harding]

test_startup.js is generated and has been missing on the charm/CI tests because the proper Make command wasn't run. Mocha, will silently ignore files it can't process/parse. Add a syntax error to the top of one of the test files and it'll run the rest of the tests.

In talking with Gary/Jeff the thought is that we should make two changes.

1. The charm/apache setup should not serve the index.html when tests are enabled for the /test directory. It should 404 if a file requested in /test is not found.

2. Change the list of included <script>test_xxx</script> to a JS array of filenames that need to be loaded. Then use Y.Get.js to load each file and check for error. If a file 404'd or failed to load, make sure we know about it.