The "virsh vcpuinfo" command results in failure when the target domain
is inactive on KVM. This patch improves this behavior by adding the
fallback to invoke virDomainGetVcpupinInfo API in case of
virDomainGetVcpus API returns error and the target domain is inactive.
Signed-off-by: NTaku Izumi <izumi.taku@jp.fujitsu.com>