Report error if setaffinity wrapper fails (Bug 32040)

Previously if the setaffinity wrapper failed the rest of the subtest
would not execute and the current subtest would be reported as passing.
Now if the setaffinity wrapper fails the subtest is correctly reported
as faling. Tested manually by changing the conditions of the affinity
call including setting size to zero, or checking the wrong condition.

No regressions on x86_64.

Reviewed-by: Florian Weimer <fweimer@redhat.com>