systemd (and maybe others) doesn't work in 2019.2

[marek-knappe]

I can fix that if someone give direction to do that (if we can drop old version support to support 2019) , but all settings for systemd will not work for saltstack 2019.2 with python3, it will generate file as follow:

[root@ip-10-0-1-132 ~] # cat /etc/systemd/user.conf.d/90-salt.conf

[u'Manager']
u'DefaultLimitCPU'=2
u'DefaultLimitNPROC'=4

It's not tested right now as docker doesn't have systemd - but at least warn people in changelog that that can be a case.