tests: Fix frontend tests (#4188), ugly work around for "Pad never loaded" (#4200)

* remote_runner.js: fix drain call (cf.
https://github.com/caolan/async/blob/master/CHANGELOG.md#breaking-changes)

* dont wait 30 seconds after remote_runner.js returned

* timeout frontend tests after 9.5 minutes to prevent travis from silently stop them

* log when not all tests finished

* prevent killTimeout to happen after last test

* log server messages to console

* remote_runner will take some time to setup sl, so this second is not necessary

* dont write to global mocha variable

* mochas `test end` event is not called when a before/beforeEach-hooks
failed, so we should only use pass/fail/pending-hooks for logging.
also some cruft removed

* pass test in `pending`-event handler

* remove some more cruft in tests/frontend/runner.js

* frontend tests: clarify why stats.tests and total differ

* move killTimeout to pass/fail/pending instead of `test end` to guarantee that it is run

* delete killTimeout on test end to prevent misleading log message

* unused variable

* fix regex

* unlikely edge case

* ensure `allowed test duration exceeded` message is printed for the last runner

* get rid of jquery.iframe.js, currently no support for IE<9

* retry up to 3 times when pad could not be loaded

* Call the logging code in stopSauce in a callback for `browser.quit()`.
This should fix cases like
https://app.saucelabs.com/tests/cb8225375d274cbcbb091309f5466cfd
Travis received all the logs and remote_runner.js exits, but there never
is a DELETE command for webdriver.

tests/frontend/index.html

@@ -18,7 +18,6 @@
     <script src="lib/expect.js"></script>
 
     <script src="lib/sendkeys.js"></script>    
-    <script src="lib/jquery.iframe.js"></script>  
     <script src="helper.js"></script>
     
     <script src="specs_list.js"></script>