Change dynamic memory requests to fixed small/large requests

If a job using the dynamic memory requests option is held for using too much memory, it will automatically double its request and release itself. It will only do this once.

Example: A job which originally requests 4000MB but tries to use more will be held, increase its request to 8000MB, and release itself. If the job then tries to use more than 8000MB, it will remain held because something else is likely going wrong.