git.osmocom.org is deprecated and will be removed at some point. Make sure we don't use it anywhere in our docker containers.
Notably this drops the following line without replacement: ADD http://git.osmocom.org/python/osmo-python-tests/patch/?id=$OSMO_PYTHON2_TESTS_COMMIT /tmp/osmo-python-tests2-commit
This was not needed, because the patch for OSMO_PYTHON2_TESTS_COMMIT will never change, it points to a commit hash (unlike checking master, where the patch can change).
