vndk-def: Fix trivial pylint errors

This commit fixes several trivial pylint errors:
dangerous-default-value, inconsistent-return-statements,
redefined-builtin, too-few-public-methods, and unused-variable.

Test: ./tests/run.sh
Change-Id: Ic24aa25e7a7aacb836f76538c7c232072e86e02e
5 files changed