qemu: Don't try to update undefined guest CPU

Calling virCPUUpdateLive on a domain with no guest CPU configuration
does not make sense. Especially when doing so would crash libvirtd.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_process.c

@@ -3815,11 +3815,6 @@ qemuProcessVerifyCPUFeatures(virDomainDefPtr def,
 {
     int rc;
 
-    if (!def->cpu ||
-        (def->cpu->mode == VIR_CPU_MODE_CUSTOM &&
-         !def->cpu->model))
-        return 0;
-
     rc = virCPUCheckFeature(def->os.arch, def->cpu, "invtsc");
 
     if (rc < 0) {
@@ -3870,6 +3865,13 @@ qemuProcessUpdateLiveGuestCPU(virQEMUDriverPtr driver,
             qemuProcessVerifyHypervFeatures(def, cpu) < 0)
             goto cleanup;
 
+        if (!def->cpu ||
+            (def->cpu->mode == VIR_CPU_MODE_CUSTOM &&
+             !def->cpu->model)) {
+            ret = 0;
+            goto cleanup;
+        }
+
         if (qemuProcessVerifyCPUFeatures(def, cpu) < 0)
             goto cleanup;