check: check dmesg log after each test

check: check dmesg log after each test

Check kernel BUG, WARNING etc. in dmesg log after each test and fail the
test if something is found. dmesg log can be found at result dir.

This check now depends on the logging of running tests in dmesg, so this
check can be done without clearing dmesg buffer nor dumping all dmesg to
a file, which can potentially eat all free space on testing host.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>