When libvirt older than 3.9.0 reconnected to a running domain started by
old libvirt it could have messed up the expansion of host-model by
adding features QEMU does not support (such as cmt). Thus whenever we
reconnect to a running domain, revert to an active snapshot, or restore
a saved domain we need to check the guest CPU model and remove the
CPU features unknown to QEMU. We can do this because we know the domain
was successfully started, which means the CPU did not contain the
features when libvirt started the domain.

https://bugzilla.redhat.com/show_bug.cgi?id=1495171Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>