qemu_process: add check for hyperv features
    
    Commit 7068b56c introduced several hyperv features.  Not all hyperv
    features are supported by old enough kernels and we shouldn't allow to
    start a guest if kernel doesn't support any of the hyperv feature.
    
    There is one exception, for backward compatibility we cannot error out
    if one of the RELAXED, VAPIC or SPINLOCKS isn't supported, for the same
    reason we ignore invtsc, to not break restoring saved domains with older
    libvirt.
    
    Signed-off-by: Pavel Hrdina <phrdina@redhat.com>