Resolve G301 expect directory permission to be 0750 or less

Resolve the following errors:
```
Error: runtime/service_test.go:315:10: G301: Expect directory permissions to be 0750 or less (gosec)
err := os.MkdirAll(stubDrivePath, os.ModePerm)
```

Start at runtime/service_test.go around line 315 and inspect the os.MkdirAll call reported by gosec as G301. Run the relevant service tests and the gosec check after updating the directory permission handling; done means the test still passes and G301 is resolved.

Written by the indexing model from the issue text.