btrfs-progs: Fix a bug in reset_nlink() which may deletes the recovered file

btrfs-progs: Fix a bug in reset_nlink() which may deletes the recovered file

In reset_nlink(), we believe rec->found_link as accurate number of the
valid links. However it only records the number of found DIR_ITEM, so we
can't use it as reliable value.

Before this patch, in some case, leaf corruption recovery will believe
there is a valid backref but don't add_link() since it can't find any
valid one and don't put it into the lost+found dir.
So the recovered inode will be considered as an orphan item without
orphan item and repair_inode_orphan_item() will add orphan item for it,
causing all the filename/filetype we recovered being a waste of time.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>