I've just done apt-get source ifupdown.

    The source contains two patches:
0001-Fix-a-crash-when-multiple-interfaces-are-specified-f.patch
0001-Unconditionally-ifup-hotplug-interfaces

    So it seems things are well done and it is enough to remove the
second patch (attached).
However, looking all over the package source, including debian/rules, I
can't find where the  patches are applied.

    Didier

From: Bjørn Mork <bjorn@???>
Subnet: Ignore link state when bringing up hotplug interfaces at boot

--- /etc/init.d/networking    2015-07-19 23:45:52.000000000 +0200
+++ /etc/init.d/networking    2016-02-15 12:00:54.600641776 +0100
@@ -107,12 +107,7 @@
                     link=${link##.*}
                     if [ -e "/sys/class/net/$link" ]
                     then
-                    # link detection does not work unless we up the link
-                    ip link set "$iface" up || true
-                    if [ "$(cat /sys/class/net/$link/operstate)" = up ]
-                    then
-                        echo "$iface"
-                    fi
+                    echo "$iface"
                     fi
                 done)
         if [ -n "$ifaces" ]