We configure ssh_ext for all present network devices (except for
some known to be irrelevant ones like the ones from VMware,
VirtualBox and Docker), instead of just enabling it for
$EXTERNAL_DEV (being eth0 by default). Retrieving the list of
available network devices is done on each of the according PRO
systems separately, so we don't enable it on sp1 for network
devices that possibly aren't available on sp2.
We also explicitly enable ssh_ext for sp2 on sp1 for loopback and
$INTERNAL_DEV (eth1 by default), so we can make sure we can
access ssh at any given time.
Michael Prokop