Deal with some "pylint: disable=" comments

Deal with some "pylint: disable=" comments

+ When possible, fix the violation.
+ Else, add a comment:
  + An explanation (if not already present) and keep disable.
  + A TODO (if not already present) and remove the disable.
- This makes tox job report more pylint violations,
  but any such violation is fixable and should be fixed.
  - Although some need to be fixed in VPP, such as enum item long names.

Change-Id: I48604b5eda070083d79dff1439620dbd9e798e1f
Signed-off-by: Vratko Polak <vrpolak@cisco.com>