In btrfs_create_tree(), if btrfs_insert_root() fails, we should
free root->commit_root.
Reported-by: NAlex Lyakas <alex@zadarastorage.com>
Signed-off-by: NTsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: NChris Mason <clm@fb.com>