dom0-updates: use qvm-service for disabling dom0 updates check

Use the same mechanism as VMs - first it's compatible with Admin API (in
contrary to flag files); second it ease handling it.

Migrate old setting on package upgrade.

dom0-updates/qubes-dom0-updates.cron

@@ -1,8 +1,6 @@
 #!/bin/bash
 
-UPDATES_DISABLE_FLAG=/var/lib/qubes/updates/disable-updates
-
-if [ -f "$UPDATES_DISABLE_FLAG" ]; then
+if [ "$(qvm-features dom0 service.qubes-update-check || echo 1)" != 1 ]; then
     exit 0
 fi
 

rpm_spec/core-dom0-linux.spec.in

@@ -165,6 +165,14 @@ fi
 
 systemctl enable qubes-suspend.service >/dev/null 2>&1
 
+# migrate dom0-updates check disable flag
+if [ $1 -ge 2 ]; then
+    if [ -e /var/lib/qubes/updates/disable-updates ]; then
+        qvm-features dom0 service.qubes-update-check ''
+        rm -f /var/lib/qubes/updates/disable-updates
+    fi
+fi
+
 %preun
 if [ "$1" = 0 ] ; then
 	# no more packages left