rkt/stop: implement --uuid-file
rkt/stop: implement --uuid-file

So the user can use the value saved on rkt run with --uuid-file-save.

euank/rkt,alban/rkt,sstabellini/rkt,jonboulle/rkt,nhlfr/rkt,lucasallan/rkt,Shashwatsh/rkt,yifan-gu/rkt,shobhit85/rkt,cab105/rkt,Shashwatsh/rkt,Wilybald/rkt,coreos/rkt,jakon89/rkt,jakon89/rkt,ybubnov/rkt,jonboulle/rkt,monstermunchkin/rkt,coreos/rkt,intelsdi-x/rkt,akshaykarle/rkt,ybubnov/rkt,alban/rkt,cab105/rkt,dgonyeo/rkt,monstermunchkin/rkt,euank/rkt,s-urbaniak/rkt,yifan-gu/rkt,joshix/rkt,lucasallan/rkt,dgonyeo/rkt,akshaykarle/rkt,kinvolk/rkt,Shashwatsh/rkt,kinvolk/rkt,monstermunchkin/rkt,shobhit85/rkt,akshaykarle/rkt,rkt/rkt,kinvolk/rkt,sstabellini/rkt,achanda/rkt,jjlakis/rkt,nhlfr/rkt,shobhit85/rkt,joshix/rkt,sgotti/rkt,intelsdi-x/rkt,achanda/rkt,ybubnov/rkt,rkt/rkt,rkt/rkt,jjlakis/rkt,Wilybald/rkt,joshix/rkt,rkt/rkt,yifan-gu/rocket,s-urbaniak/rkt,squeed/rkt,dgonyeo/rkt,sgotti/rkt,yifan-gu/rkt,yifan-gu/rocket,jonboulle/rkt,jjlakis/rkt,coreos/rkt,lucasallan/rkt,sstabellini/rkt,lucasallan/rkt,kinvolk/rkt,s-urbaniak/rkt,squeed/rkt,achanda/rkt,sgotti/rkt,intelsdi-x/rkt,yifan-gu/rocket,joshix/rkt,nhlfr/rkt,Wilybald/rkt,alban/rkt,Wilybald/rkt,squeed/rkt,jakon89/rkt,euank/rkt,cab105/rkt