btrfs: make free_fs_info() call ->kill_sb() unconditional

... and don't bother with it after btrfs_fill_super() failure -
->kill_sb() (unlike ->put_super()) will be called even if we
have not got non-NULL ->s_root.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
1 file changed