One of the last changes broke dbmaster role based ferm rules

One of the last changes broke dbmaster role based ferm rules

In particular, we allowed HOST_DB ssh to all our hosts.  That does not
make semantic sense, since the db host does not need to ssh to all the
other hosts (the reverse is true).

However, since draghi makes for a useful fallback jumphost, we now
explictly allow it.  We need to figure something out for the other role
based ferm rules.