udhcp: handle errors in read_staticlease

also gets rid of ether-aton's static buffer in ether-wake:
   text   data    bss    dec    hexfilename
 838664    441   7572 846677  ceb55busybox_old
 838650    441   7564 846655  ceb3fbusybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
5 files changed