tst-spawn-cgroup.c: Fix argument order of UNSUPPORTED message.

The arguments for "expected" and "got" are mismatched.  Furthermore
this patch is dumping both values as hex.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Florian Weimer <fweimer@redhat.com>