Updated edx video ID string

Do we really want to encourage video producers/course authors to repeatedly re-upload the same video file if the processing fails?  According to https://openedx.atlassian.net/browse/MA-137, there are 2 cases of failure: file_corrupt and pipeline_error.  In the former case (file_corrupt), re-uploading the same corrupt file wouldn't work (unless the file is corrupt due to an upload error).  In the latter case (pipeline_error), it's also unclear whether a re-upload would result in a later success.  @frrrances @lou-wang @gwprice  Any thoughts on this?