ocfs2: do not set filesystem readonly if link down

Do not set the filesystem readonly if the storage link is down.  In this
case, metadata is not corrupted and only -EIO is returned.  And if it is
indeed corrupted metadata, it has already called ocfs2_error() in
ocfs2_validate_inode_block().

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