Further pylint disables, mostly for Unused args

Many of our functions have to follow a given API, and thus we have to
keep a given signature, but pylint doesn't understand this. Therefore,
we silence this warning.

The patch does a few other cleanups.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Olivier Tharan <olive@google.com>