pdist-bootcheck: Don't loop when system disk is full

pdist/pdist-bootcheck

@@ -35,10 +35,15 @@ elif [ "$need_pdist_and_reboot" ]; then
         rm /var/run/updatecheck.reboot-triggered
         exit 1
     fi
+    if (( $(stat -f -c %f /) * $(stat -f -c %s /) /1024/1024/1024 < 10)); then
+        echo "Update and reboot required but prevented because of insufficient free disk space (<10G)"
+        exit 1
+    fi
     echo "Update and reboot required"
+    touch /var/run/updatecheck.reboot-triggered
+    sync /
     while true; do sleep 5; echo "System update in progress. Please be patient..."; done &
     netcat $(distmaster) 237
     mxgrub default
-    touch /var/run/updatecheck.reboot-triggered
     systemctl start reboot.target --job-mode=replace-irreversibly
 fi