ifupdown: correct ifstate update during 'ifup -a'. Closes 6212

ifupdown: correct ifstate update during 'ifup -a'. Closes 6212

When 'if -a' runs into an failure on an interface all further
interfaces won't be correctly updated in ifstate. This patch
inserts a new variable that only tracks the current interfaces
failure so that the write to ifstate can rely on this and not
the one for the functions return value.

Fixes https://bugs.busybox.net/show_bug.cgi?id=6212

Signed-off-by: Frank Bergmann <frank.frajasalo@googlemail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>