agent: Use SHA2 signatures also for RSA certificates
There is actually a bug in OpenSSH's ssh-agent of handling these
requests , but this change follows the way how OpenSSH clients
behave in regards to the communication with agent.
Without this change, the agent is asked to provide SHA1 signature
with certificates, which is not right if we negotiated SHA2 extensions.
Signed-off-by: Jakub Jelen <email@example.com>
Reviewed-by: Andreas Schneider <firstname.lastname@example.org>