domain_validate: drop cpu.shares cgroup check

domain_validate: drop cpu.shares cgroup check

This check is done when VM is defined but doesn't take into account what
cgroups version is currently used on the host system so it doesn't work
correctly.

To make proper check at this point we would have to figure out cgroups
version while defining a VM but that will still not guarantee that the
VM will start correctly in the future as the host may be rebooted with
different cgroups version.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>