ocfs2: set filesytem read-only when ocfs2_delete_entry failed.

In ocfs2_rename, it will lead to an inode with two entried(old and new) if
ocfs2_delete_entry(old) failed.  Thus, filesystem will be inconsistent.

The case is described below:

ocfs2_rename
    -> ocfs2_start_trans
    -> ocfs2_add_entry(new)
    -> ocfs2_delete_entry(old)
        -> __ocfs2_journal_access *failed* because of -ENOMEM
    -> ocfs2_commit_trans

So filesystem should be set to read-only at the moment.

Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
Cc: Joseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>