usr_from_src: fix missing variable
usr_from_src: fix missing variable

We were using the variable name instead of the actual variable.

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