is_interesting_input is returning too early

[flxflndy]

I'm not sure if the project is still alive, but I was reading the code saw a little improvement.
The function is_interesting_input in NaFlCore.py is returning directly after the first difference
I think it would be better to save the return value and return after the loop has finish.
Otherwise the history_bitmap is not updated correctly and more testcase must be created.