Fix conditionals for enabling QEMU sanity check
One part of the spec file checked %{kernel_arches} while the other
checked %{hostqemu}. In fact both conditions need to be valid in
order to be able to run the sanity check. Introduce an explicit
%{qemu_sanity_check} variable to express this rule.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>