Revert "systemd: preset xendriverdomain on update"

This doesn't help when xen update is installed after this one. So, deal
with it in xen %post itself.
This reverts commit f2257e1e3b.

QubesOS/qubes-issues#2141

rpm_spec/core-vm.spec

@@ -594,7 +594,7 @@ else
     services="qubes-dvm qubes-misc-post qubes-firewall qubes-mount-dirs"
     services="$services qubes-netwatcher qubes-network qubes-sysinit"
     services="$services qubes-iptables qubes-updates-proxy qubes-qrexec-agent"
-    services="$services qubes-random-seed xendriverdomain"
+    services="$services qubes-random-seed"
     for srv in $services; do
         /bin/systemctl --no-reload preset $srv.service
     done