[XFS] Stop a BUG from occurring in generic_delete_inode by preventing

transaction completion from marking the inode dirty while it is being
cleaned up on it's way out of the system.

SGI-PV: 952967
SGI-Modid: xfs-linux-melb:xfs-kern:26040a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>