mandos-keygen: Avoid comment lines from ssh-keyscan
In ssh-keyscan from OpenSSH 9.8, comment lines containing the hostname and SSH protocol banner are emitted by to standard output. Avoid this by passing the "-q" (quiet) option to ssh-keyscan.
mandos-keygen: When scanning localhost for keys, try to run "ssh-keyscan" both with and without the "-q" option. If the "-q" option worked, use the option also in the generated checker command.
Reported-By: bb <bb@tsufeki.eu> Thanks: bb <bb@tsufeki.eu> for analysis