If cpuset is disabled or not available, it libvirt must not use it.
Mainly for actions that do not need it and can use sched_setaffinity()
or numa_membind() instead, because they will fail without good reason.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1244664Signed-off-by: NLuyao Huang <lhuang@redhat.com>