stage1/host: reorder systemd-nspawn args
stage1/host: reorder systemd-nspawn args

This fixes #3215.

cab105/rkt,shobhit85/rkt,joshix/rkt,achanda/rkt,cab105/rkt,rkt/rkt,nhlfr/rkt,lucasallan/rkt,jakon89/rkt,jonboulle/rkt,joshix/rkt,joshix/rkt,lucasallan/rkt,squeed/rkt,kinvolk/rkt,coreos/rkt,coreos/rkt,intelsdi-x/rkt,achanda/rkt,jonboulle/rkt,sstabellini/rkt,rkt/rkt,jakon89/rkt,dgonyeo/rkt,coreos/rkt,dgonyeo/rkt,Shashwatsh/rkt,nhlfr/rkt,lucasallan/rkt,rkt/rkt,alban/rkt,nhlfr/rkt,dgonyeo/rkt,sstabellini/rkt,kinvolk/rkt,jakon89/rkt,cab105/rkt,achanda/rkt,alban/rkt,Shashwatsh/rkt,Shashwatsh/rkt,sstabellini/rkt,rkt/rkt,squeed/rkt,shobhit85/rkt,kinvolk/rkt,joshix/rkt,ybubnov/rkt,intelsdi-x/rkt,jonboulle/rkt,kinvolk/rkt,intelsdi-x/rkt,alban/rkt,squeed/rkt,ybubnov/rkt,lucasallan/rkt,ybubnov/rkt,shobhit85/rkt