btrfs-progs: propagate extent item errors in lowmem mode

Test 044 was failing with lowmem because it was not bubbling up the
error to the user.  This is because we try to allow repair the
opportunity to clear the error, however if repair isn't set we simply do
not add the temporary error to the main error return variable.  Fix this
by adding the tmp_err to err before moving on to the next item.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

check/mode-lowmem.c

@@ -4381,6 +4381,7 @@ next:
 		goto next;
 	}
 
+	err |= tmp_err;
 	ptr_offset += btrfs_extent_inline_ref_size(type);
 	goto next;