This changes 9pxeload to use /lib/pxe/default as a plan9.ini. Using
/cfg IMHO populates even more our crowded /, also, using just %E
makes it necessary to use one file per machine even if a single
file would be enough.
The change of load.c should probably be the addition of "default"
after the line with "%E". I include this file only to point out  the change.