rkt: stage1hash: make storeOnly false by default
rkt: stage1hash: make storeOnly false by default

This was causing URL values in `--stage1-image` to fail. Now we set it
to true only when needed.

lucasallan/rkt,achanda/rkt,alban/rkt,blixtra/rkt,s-urbaniak/rkt,shobhit85/rkt,Wilybald/rkt,yifan-gu/rkt,ybubnov/rkt,krnowak/rkt,ybubnov/rkt,joshix/rkt,lucasallan/rkt,il9ue/rkt,liugenping/rkt,alban/rkt,squeed/rkt,mike1729/rkt,Wilybald/rkt,monstermunchkin/rkt,krnowak/rkt,endocode/rkt,liugenping/rkt,matthaias/rkt,Shashwatsh/rkt,sstabellini/rkt,squeed/rkt,sstabellini/rkt,shobhit85/rkt,achanda/rkt,yifan-gu/rkt,monstermunchkin/rkt,sinfomicien/rkt,jakon89/rkt,jzelinskie/rkt,tmrts/rkt,kinvolk/rkt,dgonyeo/rkt,blixtra/rkt,sgotti/rkt,markllama/rkt,rkt/rkt,sinfomicien/rkt,rkt/rkt,akshaykarle/rkt,mike1729/rkt,linki/rkt,tmrts/rkt,s-urbaniak/rkt,rkt/rkt,matthaias/rkt,jasonchaffee/rkt,linki/rkt,kinvolk/rkt,sstabellini/rkt,joshix/rkt,cab105/rkt,jjlakis/rkt,euank/rkt,jasonchaffee/rkt,jonboulle/rkt,sgotti/rkt,coreos/rkt,linki/rkt,joshix/rkt,sgotti/rkt,jasonchaffee/rkt,jakon89/rkt,adfernandes/rkt,shobhit85/rkt,markllama/rkt,jakon89/rkt,Shashwatsh/rkt,Wilybald/rkt,kinvolk/rkt,krnowak/rkt,cab105/rkt,nhlfr/rkt,Wilybald/rkt,lucasallan/rkt,achanda/rkt,intelsdi-x/rkt,il9ue/rkt,sinfomicien/rkt,adfernandes/rkt,jjlakis/rkt,akshaykarle/rkt,ybubnov/rkt,matthaias/rkt,coreos/rkt,akshaykarle/rkt,jonboulle/rkt,rkt/rkt,tmrts/rkt,joshix/rkt,yifan-gu/rocket,kbrwn/rkt,dgonyeo/rkt,kbrwn/rkt,squeed/rkt,yifan-gu/rocket,intelsdi-x/rkt,s-urbaniak/rkt,coreos/rkt,endocode/rkt,alban/rkt,monstermunchkin/rkt,kbrwn/rkt,markllama/rkt,dgonyeo/rkt,nhlfr/rkt,adfernandes/rkt,lucasallan/rkt,yifan-gu/rocket,euank/rkt,endocode/rkt,il9ue/rkt,jonboulle/rkt,kinvolk/rkt,jzelinskie/rkt,euank/rkt,cab105/rkt,blixtra/rkt,nhlfr/rkt,jjlakis/rkt,intelsdi-x/rkt,jzelinskie/rkt,Shashwatsh/rkt,yifan-gu/rkt,liugenping/rkt,mike1729/rkt