qemu_process: add check for hyperv features

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>