selftests: lib.mk: Also install "config" and "settings"

Installed seccomp tests would time out because the "settings" file was
missing. Install both "settings" (needed for proper test execution) and
"config" (needed for informational purposes) with the other test
targets.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>