test/py: highlight warnings in the log summary

test/py: highlight warnings in the log summary

Currently, if a test emits a warning message but otherwise passes, there's
no indication of this in the log summary, which can lead to warnings being
missed. Enhance the test logic to explicitly mention warnings in otherwise
passing tests, and not to collapse the log sections for tests with
warnings, so that they're more easily seen when scanning the log.

Signed-off-by: Stephen Warren <swarren@nvidia.com>