poll: resolve use-after-free + inconsistent callbacks call
poll: resolve use-after-free + inconsistent callbacks call

This code was weird in the first place. I suspect my change will break something else
(probably the appcode that needed it). ssh_poll_ctx_free is not a good
place to send exception callbacks imho.

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