btrfs: tree-log: check btrfs_lookup_data_extent return value

Function btrfs_lookup_data_extent calls btrfs_search_slot to verify if
the EXTENT_ITEM exists in the extent tree. btrfs_search_slot can return
values bellow zero if an error happened.

Function replay_one_extent currently checks if the search found
something (0 returned) and increments the reference, and if not, it
seems to evaluate as 'not found'.

Fix the condition by checking if the value was bellow zero and return
early.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>