+ clean up FASTQs in /tmp after bwamem finishes aligning

- This is one of several immediate tasks that will help reclaim some
   of /tmp disk space that is being used with HiSeq X Ten data.  See
   [BIO-1229][1] for more details.

[1]: https://jira.gsc.wustl.edu/browse/BIO-1229
I think using temporary_input_files_queue() as a mutator in this way is surprising.  Other mutators, when passed args, change the value for that attribute to whatever was passed in, but this one appends the items to a list.  It would be more straightforward if callers used _add_to_temporary_input_files_queue() to append (which should then be renamed without the leading underscore).

temporary_input_files_queue() then can go away.