Bug#483756: insist ssh-vulnkey -a be run by the administrator upon upgrade

[jidanni@jidanni.org]

S> Not allowed access as much as "found a compromised key in ~/.ssh and warned
S> him". He has another - perfectly good and uncompromised - key he appears to
S> have been using .

I login to machine C from machines A and B. The B->C key was bad, the
A->C key was good. I use machine A then two days later B then two days
later A... unless there is lightning on my mountaintop which there
will be so I must turn everything off...