kunit: Add 'kunit_shutdown' option

This adds a new kernel command-line option, 'kunit_shutdown', which
shuts the kernel down (halts the machine) after tests are complete.

It also updates kunit_tool to use this option, and recognise the kernel
shutting down as the end of the test.

Change-Id: I5b2b25d767f7af4d80c0bc4ae2967bfaf18c73b0
Signed-off-by: David Gow <davidgow@google.com>
6 files changed