Btrfs: uninitialized data is check_path_shared()

refs can be used with uninitialized data if btrfs_lookup_extent_info()
fails on the first pass through the loop.  In the original code if that
happens then check_path_shared() probably returns 1, this patch
changes it to return 1 for safety.
Signed-off-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

fs/btrfs/inode.c

@@ -2673,7 +2673,7 @@ static int check_path_shared(struct btrfs_root *root,
 	struct extent_buffer *eb;
 	int level;
 	int ret;
-	u64 refs;
+	u64 refs = 1;
 
 	for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
 		if (!path->nodes[level])