qemu: hotplug: Remove rest of source backend if hotplug fails

When changing media using blockdev-add we need to remove the leftovers
if we didn't succeed plugging in the full chain or closing the tray.
Otherwise the data structures will be freed and thus the backing chain
members will never be unplugged.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_hotplug.c

@@ -491,6 +491,9 @@ qemuDomainChangeMediaBlockdev(virQEMUDriverPtr driver,
     if (rc == 0)
         rc = qemuMonitorBlockdevTrayClose(priv->mon, diskPriv->qomName);
 
+    if (rc < 0 && newbackend)
+        qemuBlockStorageSourceChainDetach(priv->mon, newbackend);
+
     if (qemuDomainObjExitMonitor(driver, vm) < 0 || rc < 0)
         goto cleanup;