tools: virt-host-validator is not consistent on how it treats warnings

Software environment

• Operating system: Fedora 34
• Architecture: aarch64
• kernel version: 5.12.8-300.fc34.aarch64
• libvirt version: 7.0.0 (7.0.0-4.fc34.aarch64)
• Hypervisor and version: QEMU 5.2.0 (qemu-5.2.0-7.fc34)

Description of problem

virt-host-validate doesn't treat warnings consistently. Either a warn should not cause the command to fail, or any warning should cause the command to fail.

[root@dentola]# virt-host-validate qemu
  QEMU: comprobando if device /dev/kvm exists                                   : PASA
  QEMU: comprobando if device /dev/kvm is accessible                            : PASA
  QEMU: comprobando if device /dev/vhost-net exists                             : PASA
  QEMU: comprobando if device /dev/net/tun exists                               : PASA
  QEMU: comprobando for cgroup 'cpu' controller support                         : PASA
  QEMU: comprobando for cgroup 'cpuacct' controller support                     : PASA
  QEMU: comprobando for cgroup 'cpuset' controller support                      : PASA
  QEMU: comprobando for cgroup 'memory' controller support                      : PASA
  QEMU: comprobando for cgroup 'devices' controller support                     : PASA
  QEMU: comprobando for cgroup 'blkio' controller support                       : PASA
ADVERTENCIA (Unknown if this platform has IOMMU support)
  QEMU: comprobando for secure guest support                                    : ADVERTENCIA (Unknown if this platform has Secure Guest support)
[root@dentola]# echo $?
1

Steps to reproduce

1. On a default Fedora machine, run virt-host-validate qemu
2. Check its result when warnings are present

Additional information