KVM: selftests: x86: Set supported CPUIDs on default VM

Almost all tests do this anyway and the ones that don't don't
appear to care. Only vmx_set_nested_state_test assumes that
a feature (VMX) is disabled until later setting the supported
CPUIDs. It's better to disable that explicitly anyway.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Message-Id: <20201111122636.73346-11-drjones@redhat.com>
[Restore CPUID_VMX, or vmx_set_nested_state breaks. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>