Fix leak when key exchange fails.
Fix leak when key exchange fails.

Distrotech/libssh,wangshawn/libssh,substack/libssh,mwgoldsmith/ssh,elastichosts/libssh,pouete/libssh,rofl0r/libssh,mwgoldsmith/ssh,rofl0r/libssh,Distrotech/libssh,wangshawn/libssh,nviennot/libssh,wangshawn/libssh,bigcat26/libssh-mod,Distrotech/libssh,nviennot/libssh,mwgoldsmith/ssh,jahrome/libssh,nviennot/libssh,taikoo/libssh,taikoo/libssh,DouglasHeriot/libssh,pouete/libssh,jt1/honeypot-libssh,sebadoom/libssh,mwgoldsmith/libssh,kedazo/libssh,kedazo/libssh,rofl0r/libssh,taikoo/libssh,miloj/libssh-v0.5,jt1/honeypot-libssh,miloj/libssh-v0.5,sebadoom/libssh,taikoo/libssh,jahrome/libssh,robxu9/libssh,DouglasHeriot/libssh,Distrotech/libssh,pouete/libssh,bigcat26/libssh-mod,robxu9/libssh,DouglasHeriot/libssh,elastichosts/libssh,jahrome/libssh,rofl0r/libssh,bigcat26/libssh-mod,DouglasHeriot/libssh,jahrome/libssh,pouete/libssh,robxu9/libssh,elastichosts/libssh,bigcat26/libssh-mod,kedazo/libssh,miloj/libssh-v0.5,mwgoldsmith/libssh,sebadoom/libssh,mwgoldsmith/ssh,wangshawn/libssh,substack/libssh,nviennot/libssh,jt1/honeypot-libssh,sebadoom/libssh,robxu9/libssh,substack/libssh,mwgoldsmith/libssh,miloj/libssh-v0.5,mwgoldsmith/libssh,jt1/honeypot-libssh,substack/libssh,kedazo/libssh