An xfs inode can be destroyed before log I/O involving that inode
is complete.  We need to wait for the inode to be unpinned before
tearing it down.  The patch looks big but the only real change is
adding a call to xfs_iunpin_wait() to the start of xfs_idestroy().
The rest of the patch is moving xfs_idestroy() after the pinning
routines.

Lachlan