This extends the torture API to provide a way to request
keys in different formats. This extends the keys with
private keys in the new OpenSSH format (default since
OpenSSH 7.8).
This also needs modifications to the ed25519 tests, which
do not support PEM format and expected the new format out of the
box.
Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
