Improve check for deprecated flags
Improve check for deprecated flags

Checking with getattr(object, name, [default]) provides
false positivies for flags that have their value set to None.
Checking with try: getattr(object, name) always produces
correct check values if a flag is defined in project settings.
Default values for flags are defined in the Axes default settings
so this should not alter any existing behaviour.

jazzband/django-axes,django-pci/django-axes