[syslinux] No config file and Syslinux 4 regression

[Sebastian Herbszt]

I have tested isolinux without a config file and discovered the following:

ISOLINUX 3.86 30-g9cc609c ETCD Copyright (C) 1994-2010 H. Peter Anvin et al
No DEFAULT or UI configuration directive found!
boot:

and

ISOLINUX 4.02 4.02* ETCD Copyright (C) 1994-2010 H. Peter Anvin et al
ERROR: No configuration file found

seems to hang here. no_default_msg gets printed too, but is overwritten since the cursor
doesn't seem to advance.

And if there is no config file we end up at load_config_file instead of no_config_file.

Sebastian