known_hosts: Don't leak memory in ssh_write_knownhost error paths.
known_hosts: Don't leak memory in ssh_write_knownhost error paths.

Found by Coverity.

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