virttest: supress pylint false negatives

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
.travis.yml: Add inspektor runs to virt-test travis CI job

Run inspekt after unittest runs, so we make sure
the code contributions meet coding standards and
don't have any obvious code mistakes. For now we
will only run pylint checks.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>