tests: Asyncify indentation test
tests: Asyncify indentation test

This makes it much easier to see why a test is failing. Before, a
`helper.waitFor()` failure would simply cause the test to time out.
Now an exception is displayed.

ether/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite