btrfs: do not leak reloc root if we fail to read the fs root

If we fail to read the fs root corresponding with a reloc root we'll
just break out and free the reloc roots.  But we remove our current
reloc_root from this list higher up, which means we'll leak this
reloc_root.  Fix this by adding ourselves back to the reloc_roots list
so we are properly cleaned up.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -4552,6 +4552,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
 		fs_root = read_fs_root(fs_info, reloc_root->root_key.offset);
 		if (IS_ERR(fs_root)) {
 			err = PTR_ERR(fs_root);
+			list_add_tail(&reloc_root->root_list, &reloc_roots);
 			goto out_free;
 		}