obslog: make obslog --no-origin -f work with multiple successor sets
When trying to sort multiple successor sets, this block of code used to fail with:
- TypeError: '<' not supported between instances of 'dict' and 'dict' (on py3)
- TypeError: cannot compare sets using cmp() (on py2)
So for sorted() to work properly, we need to remove dicts and sets from the data.
--HG-- branch : stable