test-obsolete-bundle-strip: add cases with prune on missing revs
Same as the previously added case, but the prune is no longer known locally.
This will mostly matter for the strip testing. Introducing the test early will
help clarify patches related to strip.
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.