File locking issue uploading against FileSystemFileStorageService

[TimLovellSmith]

This is in the postback to /packages/verify-upload

System.IO.IOException: The process cannot access the file 'C:\Users\tilovell\repo\NuGetGallery\Website\App_Data\Files\uploads\1.nupkg' because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.File.InternalDelete(String path, Boolean checkHost)
at System.IO.File.Delete(String path)
at NuGetGallery.FileSystemService.DeleteFile(String path) in c:\Users\tilovell\repo\NuGetGallery\Website\Services\FileSystemService.cs:line 15
at NuGetGallery.FileSystemFileStorageService.DeleteFileAsync(String folderName, String fileName) in c:\Users\tilovell\repo\NuGetGallery\Website\Services\FileSystemFileStorageService.cs:line 60
at NuGetGallery.UploadFileService.DeleteUploadFileAsync(Int32 userKey) in c:\Users\tilovell\repo\NuGetGallery\Website\Services\UploadFileService.cs:line 26
at NuGetGallery.PackagesController.d__23.MoveNext() in c:\Users\tilovell\repo\NuGetGallery\Website\Controllers\PackagesController.cs:line 635
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at lambda_method(Closure , Task )