ext4: avoid hang when mounting non-journal filesystems with orphan list
When trying to mount a file system which does not contain a journal, but which does have a orphan list containing an inode which needs to be truncated, the mount call with hang forever in ext4_orphan_cleanup() because ext4_orphan_del() will return immediately without removing the inode from the orphan list, leading to an uninterruptible loop in kernel code which will busy out one of the CPU's on the system.
This can be trivially reproduced by trying to mount the file system found in tests/f_orphan_extents_inode/image.gz from the e2fsprogs source tree.  If a malicious user were to put this on a USB stick, and mount it on a Linux desktop which has automatic mounts enabled, this could be considered a potential denial of service attack.  (Not a big deal in practice, but professional paranoids worry about such things, and have even been known to allocate CVE numbers for such problems.)