selftests/sysctl: Fix to load test_sysctl module

Fix to load test_sysctl.ko module correctly.

sysctl.sh checks whether the test module is embedded (or loaded
already) or not at first, and if not, it returns skip error
instead of trying modprobe. Thus, there is no chance to load the
test_sysctl test module.

Instead, this removes that module embedded check and returns
skip error only if it ensures that there is no embedded test
module *and* no loadable test module.

This also avoid referring config file since that is not
installed.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>