Only tweak-workers if there's something to tweak
Only tweak-workers if there's something to tweak

- tweak-workers should now only be called if there's something in the queue
- by moving the test outside, we don't need to call tweak-workers
- makes test-t 20 race about 3% faster

tony-o/rakudo,tbrowder/rakudo,lucasbuchala/rakudo,salortiz/rakudo,labster/rakudo,labster/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,rakudo/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,labster/rakudo,Gnouc/rakudo,tony-o/rakudo,rakudo/rakudo,Gnouc/rakudo,labster/rakudo,Gnouc/rakudo,awwaiid/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,nbrown/rakudo,salortiz/rakudo,awwaiid/rakudo,MasterDuke17/rakudo,lucasbuchala/rakudo,nbrown/rakudo,nbrown/rakudo,nbrown/rakudo,tbrowder/rakudo,salortiz/rakudo,rakudo/rakudo,softmoth/rakudo,rakudo/rakudo,tbrowder/rakudo,salortiz/rakudo,awwaiid/rakudo,nbrown/rakudo,Gnouc/rakudo,rakudo/rakudo,awwaiid/rakudo,lucasbuchala/rakudo,softmoth/rakudo,MasterDuke17/rakudo,tony-o/rakudo,rakudo/rakudo,softmoth/rakudo,tbrowder/rakudo,labster/rakudo,awwaiid/rakudo,nbrown/rakudo,lucasbuchala/rakudo,labster/rakudo,softmoth/rakudo,tony-o/rakudo,tbrowder/rakudo,lucasbuchala/rakudo,salortiz/rakudo,tony-o/rakudo,salortiz/rakudo,softmoth/rakudo,tony-o/rakudo