Correctly quote user and group names in runas script.
Correctly quote user and group names in runas script.

rake-compiler/rake-compiler-dock,rake-compiler/rake-compiler-dock,larskanis/rake-compiler-dock,larskanis/rake-compiler-dock,rake-compiler/rake-compiler-dock,rake-compiler/rake-compiler-dock,rake-compiler/rake-compiler-dock,larskanis/rake-compiler-dock