qemu: fix vcpu pinning when not all vcpus are enabled

vcpupin will fail when maxvcpus is larger than current
vcpu:

virsh vcpupin win7 --vcpu 0 --cpulist 5-6
error: Requested operation is not valid: cpu affinity is not supported

win7 xml in the command above is like below:
...
<vcpu current="3" placement="static">8</vcpu>
...

The reason is vcpu[3] and vcpu[4] have zero tids and should not been
compared as valid situation in qemuDomainRefreshVcpuInfo().

This issue is introduced by commit 34f77437, which fix recording of vCPU
pids for MTTCG.
Signed-off-by: NYi Wang <wang.yi59@zte.com.cn>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_domain.c

@@ -10700,7 +10700,7 @@ qemuDomainRefreshVcpuInfo(virQEMUDriverPtr driver,
         }
 
         for (j = 0; j < i; j++) {
-            if (info[i].tid == info[j].tid) {
+            if (info[i].tid != 0 && info[i].tid == info[j].tid) {
                 VIR_DEBUG("vCPU[%zu] PID %llu duplicates vCPU[%zu]",
                           i, (unsigned long long)info[i].tid, j);
                 validTIDs = false;