common: use fileutil.IsExecutable()
common: use fileutil.IsExecutable()

instead of direct coding of it.

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