We manually maintain the tests package's content and dependencies, so mark is as
special (matching create_manifest3.py).
(From OE-Core rev: b4bd4e7e26bb79223129abb9fb6e22e9045e3707)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>