ssh: add support for certificates from non-default views Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

ssh: handle binary keys correctly Related to https://pagure.io/SSSD/sssd/issue/3332 Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

ssh: rewrite ssh responder to use cache_req This is a bigger change since both supported commands could be rewritten for cache_req and the logic could be deleted. I decided to also split the file into more modules and follow similar pattern as with nss responder. Resolves: https://fedorahosted.org/sssd/ticket/1126 Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>