scripts: update rkt-builder version
scripts: update rkt-builder version

sstabellini/rkt,jonboulle/rkt,ybubnov/rkt,rkt/rkt,intelsdi-x/rkt,kinvolk/rkt,Shashwatsh/rkt,lucasallan/rkt,lucasallan/rkt,joshix/rkt,sstabellini/rkt,coreos/rkt,shobhit85/rkt,lucasallan/rkt,Shashwatsh/rkt,alban/rkt,coreos/rkt,jonboulle/rkt,intelsdi-x/rkt,intelsdi-x/rkt,sstabellini/rkt,rkt/rkt,dgonyeo/rkt,jonboulle/rkt,joshix/rkt,rkt/rkt,alban/rkt,Shashwatsh/rkt,ybubnov/rkt,lucasallan/rkt,dgonyeo/rkt,rkt/rkt,kinvolk/rkt,shobhit85/rkt,alban/rkt,kinvolk/rkt,joshix/rkt,shobhit85/rkt,joshix/rkt,dgonyeo/rkt,ybubnov/rkt,coreos/rkt,kinvolk/rkt