ZTS: Log test name to /dev/kmsg on Linux

Add a -K option to the test suite to log each test name to /dev/kmsg
(on Linux), so if there's a kernel warning we'll be able to match
it up to a particular test.

Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #13227