stbt batch run: Allow running inside VirtualBox shared folder

Fixes the following error:

    mkfifo: cannot create fifo ‘rawout’: Operation not permitted
    mkfifo: cannot create fifo ‘rawerr’: Operation not permitted
make check: Don't explicitly list python files to test

This increases coverage as you don't have to remember to add your python
file to the list in the Makefile.  It also saves 15 lines of Makefile.

nosetests can't check files with `-` in the name so I use the subst/
wildcard combination to filter those out.