server: fix pubkey reply for key probes
server: fix pubkey reply for key probes

Per RFC 4252, it is required to send back only one of either
SSH_MSG_USERAUTH_PK_OK or SSH_MSG_USERAUTH_FAILURE for public
key probes.

Update the handling of 'auth_pubkey_function' to send back PK_OK
instead of SSH_MSG_USERAUTH_SUCCESS for the case that the state
of the message at hand is SSH_PUBLICKEY_STATE_NONE.

With this change, it is now possible to process an initial key probe
and then subsequent signature validation using the server callbacks.

Reviewed-by: Andreas Schneider <5be00ddc76278cf6077f5047ca3384a88460c671@cryptomilk.org>

elastichosts/libssh,mwgoldsmith/libssh,taikoo/libssh,DouglasHeriot/libssh,robxu9/libssh,sebadoom/libssh,pouete/libssh,sebadoom/libssh,wangshawn/libssh,pouete/libssh,DouglasHeriot/libssh,mwgoldsmith/libssh,kedazo/libssh,taikoo/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh,wangshawn/libssh,elastichosts/libssh,kedazo/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh,Distrotech/libssh,Distrotech/libssh,DouglasHeriot/libssh,Distrotech/libssh,robxu9/libssh,pouete/libssh,nviennot/libssh,pouete/libssh,nviennot/libssh,kedazo/libssh,Distrotech/libssh,sebadoom/libssh,robxu9/libssh,nviennot/libssh,nviennot/libssh,DouglasHeriot/libssh,wangshawn/libssh,mwgoldsmith/ssh,robxu9/libssh,kedazo/libssh,taikoo/libssh,taikoo/libssh,sebadoom/libssh,mwgoldsmith/ssh,wangshawn/libssh,elastichosts/libssh