Sigh. The type of the 4th argument to application:set_env/4 has changed in Erlang 17 from being non_neg_integer() | 'infinity' to a proplist of options. And earlier versions of Erlang do not appreciate a proplist here! So just stop using it (yes, 5s timeout, but we have lots of calls to set_env/3 in the tests already and they do not seem to fail).
Fix type error (introed in 24926 I think) spotted by Dialyzer.