Ensure exec.Cmd.Path and exec.Cmd.Args[0] consistency

[karolz-ms]

Create a factory function for exec.Cmd so that we do not have to do the following all over the codebase

cmd := exec.Command("docker", args...)
// exec.Command resolves cmd.Path via LookPath but leaves cmd.Args[0] as
// the original "docker" string. Align Args[0] with the resolved Path so
// downstream consumers and child-process
// argv[0] observers see a consistent, fully-qualified command name.
if cmd.Path != "" {
	cmd.Args[0] = cmd.Path
}