Co-authored-by: Julien Muchembled <jm@nexedi.com>

We are currently experimenting re6stnet in python3 so don't install on
all machines at once.

MME init script installs unwanted ip6tables rules
which breaks re6st

It is not necessary for phones as re6st will
handle the routing. Adding masquerade interferes
with re6st routing.

format-ims must run even if there is no internet but 'slapos node boot'
is waiting for internet' so add it every minute in addition to other
places.

We really need to add support for multiple tun interface in "slapos node format".

TODO: fix the check, it should check the PCB number and not the
Amarisoft version.

This is a fixup of becf8150

For OSes with python3 older than 3.7, we build python3.7 to bootstrap
buildout.

Since we activated HMAC on the test network, there is no chance of
merging the 2 networks anymore.

Since SUSE Linux Enterprise Server 15, chrony is the default
implementation of NTP (
https://documentation.suse.com/sles/15-SP6/html/SLES-all/cha-ntp.html
).

This commit adds support for using chrony instead of ntp in SLES
versions >= 15.

See merge request !202

Opensuse names this package 'sensors' and Fedora 'lm_sensors' (see
https://www.rpmfind.net/linux/rpm2html/search.php?query=%2Fusr%2Fbin%2Fsensors)

Seems to be required in newer Amarisoft versions