Add dbxtool to 90-default.present.

As per
https://fedoraproject.org/wiki/Changes/UEFISecureBootBlacklistUpdates ,
this service should be started by default.

Signed-off-by: Peter Jones <pjones@redhat.com>
diff --git a/90-default.preset b/90-default.preset
index e89fb32..d61aabe 100644
--- a/90-default.preset
+++ b/90-default.preset
@@ -84,6 +84,10 @@
 # https://bugzilla.redhat.com/show_bug.cgi?id=1141607
 enable x2gocleansessions.service
 
+# https://fedoraproject.org/wiki/Changes/UEFISecureBootBlacklistUpdates
+#
+enable dbxtool.service
+
 enable irqbalance.service
 enable lm_sensors.service
 enable mcelog.*