jbd2: make sure ESHUTDOWN to be recorded in the journal superblock

Commit fb7c0244 ("ext4: pass -ESHUTDOWN code to jbd2 layer") want
to allow jbd2 layer to distinguish shutdown journal abort from other
error cases. So the ESHUTDOWN should be taken precedence over any other
errno which has already been recoded after EXT4_FLAGS_SHUTDOWN is set,
but it only update errno in the journal suoerblock now if the old errno
is 0.

Fixes: fb7c0244 ("ext4: pass -ESHUTDOWN code to jbd2 layer")
Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191204124614.45424-4-yi.zhang@huawei.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>