packet: Fixed linking if we build without server support.
packet: Fixed linking if we build without server support.

Thanks to Xi Wang for the patch.

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