Enabled SA update cron job on Debian.

fix #143

modoboa_installer/scripts/spamassassin.py

@@ -62,3 +62,6 @@ class Spamassassin(base.Installer):
             sudo_user=amavis_user, login=False
         )
         install("razor", self.config)
+        if utils.dist_name() in ["debian", "ubuntu"]:
+            utils.exec_cmd(
+                "perl -pi -e 's/^CRON=0/CRON=1/' /etc/cron.daily/spamassassin")