Docker vs libvirt vs firewalld conflict: get rid of firewalld

Setting up an really working libvirt environment isn't and easy task. Even worse if it's going to run inside a docker container.

Things you should know:

• Choose the right base system:
  
  anything w/ systemd - it will cause big headache sooner or later (well, it's written/maintained by a guy who doesn't know the elementary unix commands and publicly declares people with different oppionions 'racists' ...)
• KVM access:
  
  the container needs to be started w/ '--privileged' flag in order to get access to /dev/kvm device.
  without that, qemu always needs to do CPU emulation, which - of course - is sloohohow.
• Firewall utils:
  
  DONT use firewalld (get rid of it, if you did the mistake to install it!) - it will kill docker's firewall rules, and the containers will be cut off the net !
  
  In case you get strange libvirt errors like "Failed to initialize a valid firewall backend", your container probably lacks some packages: iptables, ip6tables, ebtables, dnsmasq
  
  if libvirt can't detect them, it will fall back to firewalld and fail.
• Other required packages:
• file (initrd setup tries to call it, probably for some rhel workarounds)
• libvirt-clients
• libvirt-daemon
• libvirt-daemon-system
• virtinst (in case you wanna use the virt-install command)
• nmap (symlink ncat to nc -- classic netcat won't work)
• qemu