check: log running test to dmesg

check: log running test to dmesg

We already log the running test to system logs via "logger"
but viro pointed out that we can use /dev/kmsg to insert it
into dmesg as well.  When looking at the serial console that
could be pretty useful.

Thanks to viro for the test -w suggestion too.

[Eryu Guan adds timestamp to dmesg too]

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