blkdeviotune: fix bug with saving values into live XML

When you updated some blkdeviotune values for running domain the values
were stored only internally, but not saved into the live XML so they
won't survive restarting the libvirtd.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

src/qemu/qemu_driver.c

@@ -16406,6 +16406,13 @@ qemuDomainSetBlockIoTune(virDomainPtr dom,
         if (ret < 0)
             goto endjob;
         vm->def->disks[idx]->blkdeviotune = info;
+
+        ret = virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm);
+        if (ret < 0) {
+            virReportError(VIR_ERR_OPERATION_FAILED, "%s",
+                           _("Saving live XML config failed"));
+            goto endjob;
+        }
     }
 
     if (flags & VIR_DOMAIN_AFFECT_CONFIG) {