Yet again increase the robustness of the NSURLSession tests. (#1289)
Yet again increase the robustness of the NSURLSession tests. (#1289)

Description:
These tests also used floor instead of round and it turns out the expected size was 11Mb. Oops.
nathpete-msft/WinObjC,pradipd/WinObjC,nathpete-msft/WinObjC,bbowman/WinObjC,pradipd/WinObjC,nathpete-msft/WinObjC,nathpete-msft/WinObjC,bbowman/WinObjC,ehren/WinObjC,ehren/WinObjC,pradipd/WinObjC,bbowman/WinObjC,pradipd/WinObjC,vkvenkat/WinObjC,pradipd/WinObjC,nathpete-msft/WinObjC,ehren/WinObjC,vkvenkat/WinObjC,bbowman/WinObjC,vkvenkat/WinObjC,ehren/WinObjC,vkvenkat/WinObjC,ehren/WinObjC,bbowman/WinObjC