virsh: Fix xpath queries for retrieving vcpu count

The fallback code used if virDomainGetVcpusFlags is not supported used
wrong XPath queries and basically did not work at all. Fix them to point
to the <domain> <vcpu> element instead of <vcpus> which was not present
until lately.

tools/virsh-domain.c

@@ -6157,13 +6157,12 @@ virshCPUCountCollect(vshControl *ctl,
             goto cleanup;
 
         if (flags & VIR_DOMAIN_VCPU_MAXIMUM) {
-            if (virXPathInt("string(/domain/vcpus)", ctxt, &count) < 0) {
+            if (virXPathInt("string(/domain/vcpu)", ctxt, &count) < 0) {
                 vshError(ctl, "%s", _("Failed to retrieve maximum vcpu count"));
                 goto cleanup;
             }
         } else {
-            if (virXPathInt("string(/domain/vcpus/@current)",
-                            ctxt, &count) < 0) {
+            if (virXPathInt("string(/domain/vcpu/@current)", ctxt, &count) < 0) {
                 vshError(ctl, "%s", _("Failed to retrieve current vcpu count"));
                 goto cleanup;
             }