print_nid_path has a possible buffer overflow if
struct nid_path.path values are > 256.

Avoid this and neaten the output to remove the leading ':'

Neaten debug_badness to always verify arguments.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>