CVE-2023-53187 btrfs: fix use-after-free of new block group that became unused

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix use-after-free of new block group that became unused If a task creates a new block group and that block group becomes unused before we finish its creation, at btrfscreatependingblockgroups, then when btrfsmarkbgunused ...