Fix issue of workers being put back to worker pool even nested request has not finish
Fix issue of workers being put back to worker pool even nested request has not finish

SkygearIO/skygear-server,rickmak/skygear-server,SkygearIO/skygear-server,rickmak/skygear-server,SkygearIO/skygear-server,SkygearIO/skygear-server,rickmak/skygear-server