Fix response recording for NSURLSessionDownloadTasks
Fix response recording for NSURLSessionDownloadTasks

This logic was relying on the request not getting recorded until the first call of URLSession:downloadTask:didWriteData:… Now that we begin recording from -resume, we need a different way to tell if we should record that the response has been received.

jdk89757/FLEX,fbernardo/FLEX,hugo-/FLEX,deer-hope/FLEX,otatime/FLEX,NSExceptional/FLEX,zhaoguohui/FLEX,hoaquo/FLEX,Kingside/FLEX,tttpeng/FLEX,appspector/FLEX,pjebs/FLEX,DaidoujiChen/FLEX,tttpeng/FLEX-DatabaseBrowser,Suninus/FLEX,lintaoSuper/FLEX,ramoslin02/FLEX,Flipboard/FLEX,Automatic/FLEX,Xiaobin0860/FLEX,NSExceptional/FLEX,Flipboard/FLEX,erichoracek/FLEX,sunfei/FLEX,iBcker/FLEX,evliu/FLEX,BrianBatchelder/FLEX,programming086/FLEX,msdgwzhy6/FLEX