Fix race in S17-supply/wait.t
Fix race in S17-supply/wait.t

The started thread may have been sleeping for quite a while before we started
counting the time. Could have led to occasional failures of "did we wait long
enough?"

bitrauser/roast,perl6/roast,bitrauser/roast,zostay/roast,dogbert17/roast,zostay/roast,zostay/roast,dogbert17/roast