socket: Fixed use-after-free.
socket: Fixed use-after-free.

When s->callbacks->exception() was called in ssh_socket_pollcallback()
we had a use after free bug.

pouete/libssh,wangshawn/libssh,pouete/libssh,pouete/libssh,taikoo/libssh,taikoo/libssh,sebadoom/libssh,mwgoldsmith/libssh,rofl0r/libssh,bigcat26/libssh-mod,sebadoom/libssh,Distrotech/libssh,robxu9/libssh,DouglasHeriot/libssh,nviennot/libssh,elastichosts/libssh,sebadoom/libssh,elastichosts/libssh,rofl0r/libssh,taikoo/libssh,sebadoom/libssh,nviennot/libssh,jt1/honeypot-libssh,mwgoldsmith/ssh,jt1/honeypot-libssh,Distrotech/libssh,rofl0r/libssh,wangshawn/libssh,DouglasHeriot/libssh,jt1/honeypot-libssh,mwgoldsmith/libssh,elastichosts/libssh,wangshawn/libssh,DouglasHeriot/libssh,rofl0r/libssh,mwgoldsmith/ssh,kedazo/libssh,nviennot/libssh,bigcat26/libssh-mod,bigcat26/libssh-mod,mwgoldsmith/libssh,jt1/honeypot-libssh,mwgoldsmith/ssh,pouete/libssh,wangshawn/libssh,robxu9/libssh,Distrotech/libssh,nviennot/libssh,kedazo/libssh,DouglasHeriot/libssh,mwgoldsmith/ssh,robxu9/libssh,bigcat26/libssh-mod,taikoo/libssh,kedazo/libssh,Distrotech/libssh,robxu9/libssh,kedazo/libssh,mwgoldsmith/libssh