move self.uploadPorgress check to inside of dispatch_async block

 If I used upload and download progress at the same time, sometimes I got a BAD_ACCESS error.
Connection method check self.uploadProgress is not nil and execute dispatch_async block, but inside of dispatch_async black, self.uploadProgesss can not be guaranteed it is nil or not.
So, I moved self.uploadPorgess check to inside of dispatch_async block and it is guaranteed self.uploadProgress is nil or not.