ocfs2: checkpoint appending truncate log transaction before flushing

Appending truncate log(TA) and and flushing truncate log(TF) are two
separated transactions.  They can be both committed but not checkpointed.
If crash occurs then, both transaction will be replayed with several
already released to global bitmap clusters.  Then truncate log will be
replayed resulting in cluster double free.

To reproduce this issue, just crash the host while punching hole to files.

Signed-off-by: Changwei Ge <gechangwei@live.cn>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>