Make kernel_test run from the out directory for builder

kernel_test was running from the source directory which
was clobbering kernel builds due to unclean source directory.

Copy the kernel test files to the out directory to prevent
python from putting .pyc files here.

Change-Id: Iabd6ea9f172d8e68c4723ded447b4e3c71f1b91d
Signed-off-by: Patrick Tjin <pattjin@google.com>