We get a use after free if we had a transaction to cleanup since there could be
delayed inodes which refer to their respective fs_root.  Thanks
Reported-by: NDavid Sterba <dsterba@suse.cz>
Signed-off-by: NJosef Bacik <jbacik@fusionio.com>
Signed-off-by: NChris Mason <chris.mason@fusionio.com>