disable TestFutureThen.AsyncContinuation under OSX
disable TestFutureThen.AsyncContinuation under OSX

This test may fail under OSX (with a 30% chance of failure)
thread_id might sometimes be the same (even if forcing std::launch::async policy)

samdauwe/BabylonCpp,samdauwe/BabylonCpp,samdauwe/BabylonCpp,samdauwe/BabylonCpp