plugins: linux_log_parser: check-kernel-exception: add a new cut here

The linux log parser doesn't catch all 'cut here' kernel-exceptions. Today it catches cut here looking like: '------------[ cut here ]------------' Add another multiline that can catch: '--- cut here ---' too.

https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/2bMlvywpGC6LN8eJfRQXQ4cTlEK/logs?format=html

Thanks for the change @roxell ! I've incorporated that here https://github.com/Linaro/squad/commit/76892b8510d9e2f131a13becd4a52a6db081ceac