slapos/testing: add e2e.py
e2e.py, used for slapos/software/end-to-end-testing, can be given to a testnode to run end-to-end-tests by requesting real instances.
e2e.py, used for slapos/software/end-to-end-testing, can be given to a testnode to run end-to-end-tests by requesting real instances.